Submucosal Resection of a Gastroesophageal Leiomyoma in a Dog

Signalment: 12-year-old, MN, Chihuahua

History:

This dog was previously diagnosed with inflammatory bowel disease (IBD). Five months before presentation, he presented with mild hyporexia and more frequent vomiting (from once every 6 weeks to one to two times per week).

Physical exam findings:

• No abnormal findings

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: no abnormalities

• Abdominal ultrasound: 1 cm mass in the gastric wall of the gastric body

Treatment:

Submucosal resection of a gastroesophageal mass via a gastrotomy

Outcome:

• Leiomyoma, complete excision

• Complications:

  • Vomiting and hyporexia, responsive to management with appetite stimulants, gastric protectants, and prokinetic drugs

Notes: Less aggressive resections can often result in good clinical outcomes. The mass in this dog was well circumscribed and located in the submucosal space of the gastroesophageal junction with no serosal or mucosal involvement. Considering its gross presentation and the likelihood that this was going to be either a benign or low-grade smooth muscle tumor (leiomyoma/leiomyosarcoma or gastrointestinal stromal tumor), a less aggressive surgical resection was chosen because of the high likelihood of a good oncologic outcome, and a much less risk of postoperative complications, especially in this region of the stomach. This surgery should be curative for this benign gastroesophageal leiomyoma.

Video link: https://www.youtube.com/watch?v=2NCiyakeG2k&t=37s

Tags: #leiomyoma

Preoperative ultrasound showing a mass in the gastric wall.

Intraoperative image of the mucosal-covered mass visible in the gastroesophageal junction. The mass has been exposed through a gastrotomy. The mucosa could be freely moved over the mass, but I resected the overlying mucosa en bloc with the mass.

The submucosal mass evident (arrow) after incising the mucosa around the mass. The mass was then bluntly dissected from the space with Metzenbaum scissors.

The gastric mucosal defect was closed with a single layer of 3-0 PDS in a simple continuous suture pattern. Note that a Poole suction tip was inserted into the gastric cardia and esophagus to avoid inadvertent narrowing of the lumen while closing the mucosal defect.

Once resected and the mucosal incision was closed, the gastrotomy was closed in two layers. This image shows closure of the mucosal-submucosal layer with 3-0 PDS in a simple continuous suture pattern.

Once resected and the mucosal incision was closed, the gastrotomy was closed in two layers. This image shows closure of the muscular-serosal layer with 3-0 PDS in a simple continuous suture pattern.

Postoperative specimen image of the gastroesphageal mass. This was diagnosed as a completely excised, benign leiomyoma. Surgery should be curative for this dog.

Wide Mast Cell Tumor Resection with Sentinel (Axillary) Lymph Node Mapping and Excision

Signalment: 5.5-year-old, FS, Chinese shar-pei

History:

5-week history of a cutaneous mass on the right lateral thorax. The mass was pruritic.

Physical exam findings:

• 37.0 mm x 43.5 mm cutaneous, alopecic mass caudal to the right axilla

• Axillary and superficial cervical lymph nodes normal size

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum no abnormalities

• Cytology: high-grade MCT

• Abdominal ultrasound: no significant abnormalities

Treatment:

Sentinel lymph node mapping and excision; and wide MCT resection and primary closure of the defect.

Outcome:

• High grade III MCT (mitotic count 10/10 hpf) with complete histologic excision (lateral margins of 4.7 mm to 13.0 mm, and deep margins on 12.0 mm), and HN2 lymph node (i.e., early metastasis)

• Complications:

  • None

Notes: The prognosis for this dog is unknown in some respects.

In the initial study reporting on the low/high grading scheme for MCTs, a median survival time of only 4 months was reported following surgical resection; however, this median survival time tripled when surgery was combined with chemotherapy.

More recent studies investigating the outcome following surgery alone for dogs with non-metastatic, high grade MCTs have shown more promising median survival times of 545 days, 899 days, and 1,046 days, with 1- and 2-year survival rates of 79% and 73%, respectively, in the latter study.

Two studies have shown no significant different in outcomes for dogs with HN2 (early) lymph node metastasis when treated with surgery alone versus surgery and chemotherapy; however, the majority of these dogs had high-grade II MCTs and not grade III MCTs.

So, what do we do with high-grade III MCTs with HN2 lymph node metastasis?

This dog is unfortunately a breed predisposed to high grade MCTs. Unfortunately, she developed a second mass on the right lateral flank (distant to the surgery site) within 1 month of surgery, and this was cytologically confirmed as a MCT. She is currently being treated with Palladia by our medical oncology team.

Tags: #MCT #SLN #SLNmapping

Preoperative sentinel lymph node (SLN) mapping radiograph following 4-quadrant, peritumoral injection of 0.5 ml of Omnipaque in each quadrant. While not as easy to detect as some SLN mapping procedures, there is contrast enhancement of the ipsilateral axillary lymph node (arrow).

Intraoperative SLN mapping with 4-quadrant, peritumoral injection of 0.5 ml sterile methylene blue in each quadrant. I typically do these injections on the border of the MCT but some surgeons prefer to do these injections 5-10 mm away from the MCT to minimize MCT degranulation and the effects that this may have on surgical margins.

Intraoperative SLN mapping with 4-quadrant, peritumoral injection of 0.5 ml sterile methylene blue in each quadrant. I typically do these injections on the border of the MCT but some surgeons prefer to do these injections 5-10 mm away from the MCT to minimize MCT degranulation and the effects that this may have on surgical margins.

Intraoperative SLN mapping with 4-quadrant, peritumoral injection of 0.5 ml sterile methylene blue in each quadrant. I typically do these injections on the border of the MCT but some surgeons prefer to do these injections 5-10 mm away from the MCT to minimize MCT degranulation and the effects that this may have on surgical margins.

Intraoperative SLN mapping with 4-quadrant, peritumoral injection of 0.5 ml sterile methylene blue in each quadrant. I typically do these injections on the border of the MCT but some surgeons prefer to do these injections 5-10 mm away from the MCT to minimize MCT degranulation and the effects that this may have on surgical margins.

Following resection of the MCT with 2 cm lateral margins and part of the latissimus dorsi muscle for deep margins, blue coloured lymphatics could be seen heading in the direction of the axilla (see middle finger of assistant).

Once the blue coloured sentinel (axillary) lymph node was identified, this was excised with a LigaSure.

Immediate postoperative image following primary closure of the surgery site.

Lip Resection and Facial Axial Pattern Flap Reconstruction with Sentinel Lymph Node Mapping and Excision in a Dog with a High-Grade Mast Cell Tumor

Signalment: 10-year-old, FS, greyhound

History:

This dog originally presented to our medical oncology service in mid February 2025 with a 2-month history of a left rostral lip mass. A mast cell tumor (MCT) was diagnosed on fine-needle aspirate cytology, and a low grade MCT (mitotic count 0/10 hpf) was diagnosed histologically following a punch biopsy. She was transferred to our surgery service 5 weeks later for discussion on further staging (with sentinel lymph node mapping) and surgical options.

Physical exam findings:

• 30.5 mm x 38.9 mm left rostral lip mass

• Mandibular lymph nodes normal size bilaterally

Diagnostic and clinical staging tests:

• CBC: mild thrombocytopenia

• Serum biochemistry: mildly increased creatinine with high normal BUN and SDMA

• Cytology: MCT

• Histopathology: low grade MCT with a mitotic count of 0/10 hpf

Treatment:

Sentinel lymph node mapping and excision; and wide MCT resection with lip reconstruction using a facial axial pattern flap.

Note: I personally prefer the term “facial axial pattern flap” for this flap but it is also called an angular oris axial pattern flap. I prefer facial axial pattern flap as the direct arterial supply is not solely the angular oris artery but also the superior and inferior labial arteries, all of which are separate branches of the facial artery.

Outcome:

• High grade III MCT (mitotic count 17/10 hpf) with complete histologic excision (lateral margins of 0.7 mm to 16.0 mm, and deep margins on 9.8 mm), and HN0 lymph node (i.e., no metastasis)

• Complications:

  • Flap edema. This is a common complication with the facial axial pattern flap, occurring in 89% of dogs and 100% of cats.

  • Distal flap necrosis and partial incisional dehiscence. While this is less common than edema, partial incisional dehiscence and distal flap necrosis are reported in 30% and 22% of dogs, respectively. I was concerned about the possibility of distal flap necrosis because of the conformation of the head of this dog; she had a long nose and a relatively short lateral face, which, combined with a rostral lip defect, meant that the flap dimensions were relatively smaller and this needed to be transposed a greater distance becaiuse of the length of the nose and the rostral location of the defect. The distal flap necrosis was debrided and managed as an open wound, resulting in full thickness loss of the rostral 50% of the flap/lip.

  • Surgical site infection

Notes: In one study investigating the accuracy of pre-treatment biopsy in dogs with MCTs (Shaw et al, Vet Comp Oncol, 2018), the authors found an overall concordance rate of 96% based on the Patnaik grading system, and an overall concordance rate of 92% based on the Kiupel grading system. The accuracy of the various biopsy techniques (wedge, punch and needle core) when compared with excisional biopsy was 92%, 100% and 100%, respectively, based on the Patnaik grading system, and 90%, 95% and 100%, respectively, based on the Kiupel grading system. Of the cases with discordant results, the pre-treatment biopsies tended to underestimate the grade of the tumor. The authors concluded that pre-treatment biopsies are sufficiently accurate for differentiating low-grade from high-grade MCTs, regardless of biopsy technique or tumor location.

Obviously, while this is generally true, the preoperative biopsy was not accurate in this particular dog considering a low grade MCT with a mitotic count of 0/10 hpf was diagnosed preoperatively and it was definitively diagnosed with a high-grade III MCT with a mitotic count of 17/10 hpf postoperatively. The latter is more consistent with MCTs in a perioral or muzzle location as the majority of these have a higher histologic grades with a more aggressive biological behaviour. In this case, there was no evidence of lymph node metastasis, so the prognosis should be good for this dog. Studies investigating the outcome following surgery alone for dogs with non-metastatic, high grade MCTs have shown more promising median survival times of 545 days, 899 days, and 1,046 days, with 1- and 2-year survival rates of 79% and 73%, respectively, in the latter study.

Tags: #MCT #SLN #SLNmapping #facialaxialpatternflap #reconstruction #distalflapnecrosis

Sentinel lymph node mapping was performed with four-quadrant, peritumoral injection of 2 ml Omnipaque. Radiographs taken at 1 min show contrast enhancement of the ipsilateral medial and lateral mandibular lymph nodes (arrows). Note the contrast-enhanced lymphatics draining into these lymph nodes.

Sentinel lymph node mapping was performed with four-quadrant, peritumoral injection of 2 ml Omnipaque. Radiographs taken at 1 min show contrast enhancement of the ipsilateral mandibular lymph nodes (arrow).

The margins of the tumor, 2 cm lateral margins around the MCT, and the borders of the facial axial pattern flap were marked with a sterile marker pen.

The facial axial pattern flap was raised before resection of the lip MCT. The borders for this flap are along the ventral aspect of the zygomatic arch dorsally, along the ventral aspect of the mandible ventrally, and then these two incisions are connected caudally at the level of external ear canal. You can appreciate how short this flap is relative to the length of the nose.

The flap was undermined below the level of the panniculus muscle, preserving the subdermal plexus. The mandibular lymph nodes were visible after the flap was raised.

The medial and lateral mandibular lymph nodes were extirpated using a LigaSure. Note that intraoperative sentinel lymph node mapping was not used because we knew that the mandibular lymph nodes would be well exposed with this approach.

The facial axial pattern flap after it was completely raised.

I was feeling a little more confident after transposing the facial axial pattern flap into the likely defect, as can be seen with the rostral extent of the flap in this image.

The flap was protected with moistened gauze swabs, and the lip MCT was resected with 2 cm lateral margins and full thickness lip for deep margins.

Gross appearance after full thickness resection of the lip MCT with 2 cm lateral margins.

The rostroventral corner of the flap was sutured initially. Note that haired lip will now form the medial aspect of the reconstructed lip.

The facial axial pattern flap was then sutured to the residual labial mucosal margin to complete the intraoral closure.

The lateral aspect of the flap was then sutured into position. The tension was highest on the rostral aspect of the flap, as well as the rostral aspect of the donor site closure; both of these areas eventually underwent necrosis and dehiscence.

Appearance of the facial axial pattern flap 1 day after surgery. Notice the edema and swelling in the flap, which is common in facial axial pattern flaps (occurring in 89% of dogs).

8 days after surgery, the area of the flap indicated by the arrows is slightly darker and has a more leathery feel, indicating likely distal flap necrosis.

The area of distal flap necrosis extended after a further 4 days (12 days postop) (arrows). This was debrided, cultured, and treated with empirical (and, later, culture-directed) antibiotics.

Gross appearance of the dog 14 days after her original surgery, and 2 days after her debridement. Her open wound continues to heal by second intention and, while cosmesis is less than desirable, she is functioning completely normal and has returned to her normal quality of life.

Orbitectomy for a Dog with a Grade I Multilobular Osteochondrosarcoma

Signalment: 3.5-year-old, FS, golden retriever

History:

This dog was referred after a 2-month history of right-sided conjunctivitis and increased intraocular pressure (21-25 mm Hg) progressing to exophthalmos with an inability to retropulse the right eye. A CT scan was performed which showed a well-circumscribed osseous mass arising from the medial orbital bone.

Physical exam findings:

• Mild to moderate right-sided exophthalmos

• Inability to retropulse right eye

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: no abnormalities

• CT scan: 3.2 cm x 3.4 cm x 3.9 cm osseous mass arising from the medial aspect of the right orbit, with mild enlargement of the right medial retropharyngeal lymph node. No evidence of lung metastasis.

Treatment:

Orbitectomy combined with resection of the zygomatic arch and coronoid process of the mandible.

Outcome:

• Grade I multilobular osteochondrosarcoma (MLO) with complete excision (bone margins: 20.0 mm to 30.0 mm; deep margins: 11.0 mm)

• Complications:

  • Blindness (OD), immediate. This was expected to some degree because of prolonged retraction on the optic nerve and vessels to expose the bone margins for resection of the mass.

  • Sneezing and difficulty opening jaw, 6 weeks postop. The cause for these remain undiagnosed and unresolved. While local tumor recurrence is a possibility, I think this is highly unlikely considering that this tumor was completely excised with very good surgical and histologic margins, and that this is a grade I MLO (which are typically slow growing tumors). A repeat CT has been recommended but this has not been done yet.

Video link: https://www.youtube.com/watch?v=eBrdiKihhZA&t=370s

Tags: #MLO #orbitectomy

Preoperative CT scan showing a large osseous mass arising from the medial aspect of the right orbit.

Preoperative CT scan showing a large osseous mass arising from the medial aspect of the right orbit. Note that this mass extends to the orbital bone overlying the frontal lobe of the brain.

3D reconstruction showing the large orbital mass. These reconstructions are very helpful in surgical planning, especially the approach (in this case, zygomatic arch resection and resection of the coronoid process of the mandible) and the margins (in this case, knowing that we would see brain and hence use a more delicate instrument to make the osteotomies in this region).

The initial surgical approach involved a skin incision along the zygomatic arch and extending on to the dorsolateral aspect of the caudal muzzle.

Electrosurgery was used to incise and elevate the temporal (pictured) and masseter muscles from the dorsal and ventral aspects of the zygomatic arch, respectively.

Soft tissues attached to the medial aspect of the zygomatic arch were freed using a periosteal elevator.

The first step to exposing the orbit is a zygomatic arch resection. Once the zygomatic arch is exposed and freed of all its soft tissue attachments, the caudal zygomatic bone osteotomy was performed with a sagittal saw. The periosteal elevator is positioned to protect the deeper soft tissues from iatrogenic trauma from the saw blade.

The rostral zygomatic arch resection was completed with a sagittal saw and osteotome and mallet. This osteotomy was done in such a way that a portion of the caudal maxilla was included in the osteotomy, but dorsal to the teeth.

The completed zygomatic arch resection before removal of the zygomatic arch. I do not replace the zygomatic arch after surgery. There is no functional need for it and I very rarely see a cosmetic defect as a result of its absence.

The orbit mass was easily exposed after dissecting through the superficial soft tissues; however, the caudal aspect of the mass and caudal orbit were difficult to visualize because of the vertical ramus of the mandible.

The coronoid process of the mandible was osteotomized with a sagittal saw dorsal to the temporomandibular joint to improve visualization of the caudal orbit.

Following the removal of the coronoid process of the mandible, the exposure of the caudal orbit was markedly improved.

I wanted to save the eye, which we did anatomically, but the dog was blind in this eye after surgery. I suspect this was a result of protracted and marked retraction of the caudal globe structures (vessels and optic nerve) during resection of the mass. The majority of the dorsal osteotomy was done with a piezotome in an effort to reduce iatrogenic trauma to the underlying brain; however, while accurate and precise, a peizotome is a painfully slow technique to do osteotomies, even in thin bone such is in this region.

Intraoperative image of the orbitectomy site following removal of the orbital mass from the surgical field.

Bleeding from the meninges was controlled with hemostatic foam.

The wound was then closed primarily in three layers: temporal and masseter muscle fascia, subcutaneous, and skin.

Postoperative specimen image of the resected orbital mass. The mass had a small attachment to the orbital bone, which meant that bone margins were easier to achieve than if this had a broad-based attachment to the bone. Additional caudal margins were obtained because I was not satisfied with my original margins. Histologically, this was a complete excision with the narrowest histologically tumor-free margins being 11 mm.

Immediate postoperative CT scan showing the extent of the orbitectomy along the rostral aspect of the surgical field.

Immediate postoperative CT scan showing the extent of the orbitectomy along the caudal aspect of the surgical field at the level of the frontal lobe of the brain.

Reconstructed CT view of the orbitectomy.

Day 1 postoperative appearance. This swelling and bruising took over 1 week to subside. The swelling made initial assessment of eyesight difficult, but the dog did not have a menace reflex initially and had not regained a menace reflex by week 6 after surgery.

Total Unilateral Maxillectomy via a Combined Approach for Resection of a Biologically High-Grade but Histologically Low-Grade Fibrosarcoma

Signalment: 7.5-year-old, MN Siberian husky

History:

This dog presented with a 1-month history of a left-sided muzzle mass. He did not have any other clinical signs associated with this mass.

Physical exam findings:

• 43.5 mm x 50.4 mm firm and fixed mass extending along the left muzzle from rostral to the orbit to the rostral aspect of the muzzle

• No involvement of the oral cavity

• Mandibular lymph node normal size on palpation

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: mildly increased ALT, ALP, and GGT

• Punch biopsy: sarcoma

• CT scan: left-sided soft tissue mass extending along the lateral aspect of the muzzle. No evidence of either lymph node or lung metastasis.

Treatment:

Total unilateral maxillectomy via a combined dorsolateral skin and intraoral approach, including en bloc resection of the skin overlying the mass. A biologically high-grade but histologically low-grade fibrosarcoma was suspected based on its presentation and CT appearance, so 3 cm soft tissue and bone margins were used for resection, including a rostral orbitectomy. We had initially planned to reconstruct the soft tissue defect with a facial axial pattern flap; however, after resection, this was not required as we were able to preserve the ventral lip margin.

Outcome:

• Hi-lo fibrosarcoma with complete excision (skin margins: 7.2 mm to 12.0 mm; bone margins: 6.4 mm to 20.0 mm)

• No complications

Video link: https://www.youtube.com/watch?v=6bFNQldai0Q&t=1042s

Tags: #hiloFSA #FSA #orbitectomy #maxillectomy

Preoperative CT scan showing a soft tissue mass extending along the lateral aspect of the left muzzle. This is a more consistent presentation for a hi-lo fibrosarcoma than any other tumor type, and correlated with the preoperative biopsy results.

Preoperative CT scan showing a soft tissue mass extending along the lateral aspect of the left muzzle. There was a small amount of bone involvement (arrow), but otherwise this was entirely a soft tissue mass. This is a more consistent presentation for a hi-lo fibrosarcoma than any other tumor type, and correlated with the preoperative biopsy results.

While the skin overlying the mass was freely movable, this was resected en bloc with the mass because of the high likelihood that this was a hi-lo fibrosarcoma, which is associated with a high risk of local tumor recurrence. Note that the borders for a planned facial axial pattern flap have been marked with a sterile marker pen; however, we did not end up using this flap for reconstruction of the lip defect.

The soft tissue dissection is then continued deeply to the level of the maxilla and full thickness through the lips with 3 cm soft tissue margins in the subcutaneous space.

An intraoral incision is made along the gingival margin, connecting the skin incision to create a bipedicle flap (near my left thumb). Pictured is an incision being made along the medial aspect of the dental arcade into the mucoperiosteum of the hard palate.

The mucoperiosteum is then elevated and reflected medially to expose the palatine bone for its osteotomy.

A sagittal saw was used to osteotomize the rostral aspect of the zygomatic arch and caudal maxilla.

A sagittal saw was used to continue the osteotomy along the dorsal midline of the maxilla.

Once the dorsal osteotomy was completed, this was then continued rostrally between the left canine and corner incisor teeth.

The sagittal saw was then used to perform an osteotomy along the hard palate bone.

Finally, an osteotome and mallet were used for the osteotomy within the rostral aspect of the orbit, connecting the dorsal maxilla and palatine osteotomies. This is typically done with an osteotome and done last as this cut has the greatest potential for brisk bleeding from the maxillary artery. While techniques have been described to pre-ligate the maxillary artery, I rarely find this necessary.

Medial soft tissue attachments to the resected maxillary bone are then transected; in this case, with a LigaSure.

The resected maxillectomy segment immediately prior to being removed from the surgical field.

Appearance of the maxillary defect following removal of the maxillectomy segment for the surgical field.

The mucosa and submucosa of the lip was split to create a labial mucosal-submucosal flap, and then this was sutured to the submucosa of the mucoperiosteum. This is easier to do from the lateral skin incision.

The mucosa and submucosa of the lip was split to create a labial mucosal-submucosal flap, and then this was sutured to the submucosa of the mucoperiosteum. This is easier to do from the lateral skin incision.

Intraoral appearance of the palatine closure.

I had originally planned to close the lateral muzzle defect with a facial axial pattern flap; however, we were able to preserve the ventral aspect of the upper lip and close this defect primarily.

Primary closure of this defect resulted in elevation of the caudal aspect of the upper lip but I preferred this to the potential complications associated with flap reconstruction of this defect.

Postoperative specimen image of the maxillectomy, lateral aspect. This was confirmed as a hi-lo fibrosarcoma with the narrowest histologic tumor-free margins being 6.4 mm.

Postoperative specimen image of the maxillectomy, medial aspect. This was confirmed as a hi-lo fibrosarcoma with the narrowest histologic tumor-free margins being 6.4 mm.

Appearance of the dog 1 day postoperatively.

Subcutaneous Biologically High Grade and Histologically Low Grade Fibrosarcoma Resection with Orbitectomy and Rotation Flap Reconstruction

Signalment: 7-year-old, MN bernadoodle

History:

This dog initially presented to me in late November 2023 with a rapidly growing subcutaneous mass, measuring 36.2 mm x 58.4 mm, on the dorsal to right dorsolateral aspect of the head. An incisional biopsy of the mass was read out as a fibroma. Wide resection of the mass was done a week later; histopathology of the mass was consistent with an incompletely excised (on the deep margin) biologically high grade and histologically low grade (so called hi-lo) fibrosarcoma.

The dog presented for a recheck exam in mid-January 2025 because of concern for a local recurrence. There was a palpable mass in the region of the surgical scar and a subsequent incisional biopsy confirmed a hi-lo fibrosarcoma. Three days prior to his planned surgery, a second mass appeared along the ventral aspect of the right lower eyelid. This was not physically connected to the recurrent mass. While a biopsy of this mass was discussed, his owner elected to proceed with surgery under the assumption that this was also a hi-lo fibrosarcoma.

Physical exam findings:

• Recurrent firm mass dorsomedial to the right upper eyelid

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: mildly increased amylase and lipase

• Punch biopsy: hi-lo fibrosarcoma

• Three-view thoracic radiographs: possible but unlikely lung metastasis

• CT scan: intrathoracic abnormality was an anomaly in the cranial vena cava, no evidence of lung metastasis; but evidence of bone invasion into the right frontal sinus

Notes:

A few things to consider with this case:

• If the biologic behaviour of the mass (e.g., rapidly growing in this case) does not match the biopsy results (e.g., fibroma), then you should advise the owner that a more aggressive surgery may be required and a different postoperative biopsy result expected because the biologic behaviour and the biopsy results do not match.

• Hi-lo fibrosarcomas are relatively common in the oral cavity, particularly in large breed dogs and especially in retriever breeds. This is my first case of a hi-lo fibrosarcoma in a location other than the oral cavity.

Treatment:

Wide surgical resection with 3 cm lateral margins and an orbitectomy-craniectomy for deep margins, including enucleation, and reconstruction with a rotation flap from the lateral face.

Outcome:

• Hi-lo fibrosarcoma with complete excision (lateral margins varying from 2.5 mm to 2.0 cm and deep margins clean)

• Distal flap necrosis

Video link: https://www.youtube.com/watch?v=4c6EIQnm73I&t=773s

Tags: #hiloFSA #FSA #orbitectomy #sinusectomy #reconstruction #rotationflap #distalflapnecrosis

Preoperative CT scan showing extension of the mass through the frontal bone into the frontal sinus (arrow). This surprised me to some degree. When discussing the possibility of local recurrence following incomplete histologic excision, I also consider what is deep to this margin and how likely are residual tumor cells, if actually present, to be able to propagate into a recurrent tumor. For this dog, I thought that this was unlikely considering the tissue deep to his original tumor was bone. But then this was a hi-lo fibrosarcoma and these are one of the most locally aggressive tumors in dogs.

Intraoperative image of the dog immediately prior to starting surgery. Note the subcutaneous masses along the medial aspect of the upper eyelid (recurrent mass) and lower eyelid. Lateral margins of 2 cm and 3 cm have been marked with a sterile marker pen.

An incision was done along the marked 3 cm lateral margins circumferentially around both the lower and upper eyelid masses.

This incision was then continued deeply to the level of the frontal sinus, zygomatic, and caudal maxillary bones.

A sagittal saw was used for the dorsal (frontal sinus) osteotomy.

The next step was an osteotomy along the zygomatic arch.

Once the zygomatic arch osteotomy was completed, the optic vessels and nerve were sealed and transected with a LigaSure.

Retraction of the caudal eye structures exposed the orbital bone to allow for an orbitectomy with a sagittal saw. This can also be done with a pneumatic burr or piezotome, but the sagittal saw is the most efficient of these power devices for performing these osteotomies.

The caudal aspect of the orbitectomy was completed with an osteotome and mallet.

Appearance of the defect following completion of the wide tumor resection with en bloc orbitectomy-sinusectomy for deep margins.

A facial axial pattern flap was considered for closure of this defect; however, this flap was partially compromised because of the resection. As a result, a rotation flap from the lateral aspect of the face and neck was used for reconstruction. The borders of this flap were initially marked with a sterile marker pen (arrows).

An incision was then performed along the border of the rotation flap.

The rotation flap was then raised deep to the panniculus muscle to preserve the subdermal plexus. This is a random or subdermal plexus flap and so the blood supply is entirely dependent on preservation of the subnormal plexus blood supply rather than a named artery and vein like in axial pattern flaps.

The rotation flap was then rotated into the defect.

The position of the rotation flap was initially secured with tagging sutures.

The rotation flap was then sutured into place in two layers with a 2-0 Monocryl simple continuous suture pattern in the subcutaneous layer and staples for the skin layer.

Postoperative specimen image with inked margins to help orientate the pathologist. Note the tumor extending through the frontal bone into the frontal sinus in the bottom left of the image.

Approximately 5 days after surgery, a well demarcated section of skin on the distal aspect of the flap was firm and leathery. This is classic for distal flap necrosis.

After anesthetizing the dog and clipping the area, there section of flap necrosis, again well demarcated, can be seen extending caudally along the flap border.

The necrotic areas of the flap were debrided and the flap resutured into position in two layers, 2-0 Monocryl simple continuous suture pattern in the subcutaneous layer and 2-0 Nylon in cruciate and continuous Ford interlocking patterns for the skin layer.

Chest Wall Resection and Reconstruction in a Dog with a Grade I Chondrosarcoma

Signalment: 14-year-old, MN mixed breed dog

History:

A firm mass was noted by the owner on the left ventrolateral chest wall and the mass had slowly grown over a 3-month period.

Physical exam findings:

• 58.9 mm x 42.7 mm firm and fixed mass on the left ventrolateral cranial thoracic wall

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: mildly increased ALP

• Fine-needle aspirate: suspected sarcoma

• CT scan: Soft tissue mass, 4.4 cm x 5.0 cm x 5.8 cm, centred around the proximal aspect of the costochondral junction of the left fourth rib with possible involvement of the fifth rib. No evidence of lung metastasis.

Notes:

The owners and I had a detailed discussion about the difference in prognosis between primary rib osteosarcoma (median survival time 120-190 days with surgery alone and 240-290 days with surgery and chemotherapy) and chondrosarcoma (median survival time 1080 to >3820 days with surgery alone), the two most common primary rib tumors in dogs. We also discussed the two main reasons to do a preoperative biopsy: 1. If the results change what me, as the clinician, recommends, or 2. If the results change the owners’ willingness to proceed with treatment. The results of a biopsy would not change my treatment recommendation as a chest wall resection and reconstruction would be recommended regardless of tumor type; however, with the marked differences in prognosis, the biopsy results may change the willingness of the owner to proceed with chest wall resection. In this case, the owners decided to proceed with surgery without doing a preoperative biopsy.

Treatment:

Chest wall resection with one normal rib cranially and caudally (third through sixth, four ribs in total) for cranial and caudal margins, 3 cm of normal rib dorsal to the tumor, and the costosternal junction (with an ipsilateral median sternotomy of the third through sixth sternebrae) for ventral margins. The chest wall defect was reconstructed with Marlex mesh, latissimus dorsi muscle flap, and pectoral muscle flap.

Outcome:

• Grade I primary rib chondrosarcoma with complete histologic excision with ventral, dorsal, cranial, and caudal margins of 6.5 cm, 5.5 cm, 1.0 cm, and 1.4 cm, respectively.

• No complications

Video link: https://www.youtube.com/watch?v=QQZOzGtYh7o (latissimus dorsi muscle flap only)

Tags: #ribCSA #chestwall #chestwallresection #chestwallresection #chondrosarcoma

Axial CT scan showing a left ventrolateral (costochondral junction) mass. The costochondral junction is a common location for primary rib tumors.

A multiplanar reconstruction of the CT scan shows that the rib mass is arising from the left fourth rib and there was partial involvement of the fifth rib. As a result, four rather than three ribs were planned to be resected.

A diagonal skin incision was made from cranioventral to caudodorsal, in the same direction as the latissimus dorsi muscle. This provides the best exposure of this muscle for dissecting it free and raising it for later reconstruction.

A Harmonic Scalpel was used to free the ventral border of the latissimus dorsi muscle.

Once the ventral border of the latissimus dorsi was freed, it was elevated (pictured) and undermined. There are perforating vessels between the deeper chest wall and latissimus dorsi muscle which need to be sealed and transected.

Once the ventral border of the latissimus dorsi was freed, it was elevated and undermined (pictured). There are perforating vessels between the deeper chest wall and latissimus dorsi muscle which need to be sealed and transected.

The latissimus dorsi muscle inserts on the 13th rib and this caudal border is then incised with a Harmonic Scalpel. Once this is elevated, the dorsal border (arrow) of the latissimus dorsi muscle is best visualized from the deep aspect of the muscle rather than superficially.

The dorsal border of the latissimus dorsi muscle was then incised and freed with a Harmonic Scalpel.

The latissimus dorsi muscle after the ventral, caudal, and dorsal borders were freed. Note the skin hooks used to atraumatically manipulate the muscle flap; these are made from hypodermic needles.

The first step for the chest wall resection, after raising the latissimus dorsi muscle, is performing an intercostal thoracotomy caudal to the first normal rib caudal to the rib tumor. In this case, the 6th-7th intercostal space.

Once the caudal intercostal thoracotomy is completed, the rib is retracted laterally to directly visualize the primary rib tumor, assess whether there is any obvious adhesion between the rib tumor and intrathoracic structures (such as the lung lobe or pericardium), and determine if any changes need to be made to the planned dorsal and ventral margins.

Once the caudal intercostal thoracotomy is completed, the rib is retracted laterally to directly visualize the primary rib tumor (arrow), assess whether there is any obvious adhesion between the rib tumor and intrathoracic structures (such as the lung lobe or pericardium; none in this case), and determine if any changes need to be made to the planned dorsal and ventral margins (none in this case).

Intraoperative image following completion of the caudal intercostal thoracotomy.

To prophylactically control bleeding from the intercostal vessels, a ligature (0 PDS) was passed circumcostally around the proximal aspect of the 6th rib.

To prophylactically control bleeding from the intercostal vessels, a ligature (0 PDS) was passed circumcostally around the proximal aspect of the 6th rib.

To prophylactically control bleeding from the intercostal vessels, a ligature (0 PDS) was passed circumcostally around the proximal aspect of the 6th rib.

Once the circumcostal ligature is completed, the rib is ostectomized distal to the circumcostal ligature with bone cutters.

It ended up that I did not have enough Weeties to ostectomize the ribs with bone cutters and subsequently had to resort to using a sagittal saw for the rib ostectomies.

The intercostal muscles between the 5th and 6th ribs were then transected with a Harmonic Scalpel.

The circumcostal ligature was secured and an ostectomy of the proximal aspect of the 5th rib was performed with a sagittal saw. This was repeated for the fourth and third ribs.

A second intercostal thoracotomy was performed cranial to the first normal rib cranial to the rib tumor (3rd rib), in this case a 2nd-3rd intercostal space.

The rib segment was reflected ventrally. The internal thoracic artery was sealed and transected with a Harmonic Scalpel. This allowed exposure of the ventral midline of the sternum. A median sternotomy was performed with a sagittal saw between the 3rd and 6th sternebrae, and the ipsilateral half of these sternebrae were resected en bloc with the chest wall segment. This was done because the rib mass was ventrally located and resecting the costochondral junction was deemed necessary to obtain adequate ventral margins, similar to what is done for resection of appendicular bone tumors.

The chest wall defect of four ribs following removal of the resected chest wall segment.

A double layer of Marlex was secured to the corners of the chest wall defect with tagging sutures (using 0 Prolene) to place the mesh under a degree of tension to provide rigidity to the chest wall reconstruction.

The mesh was then sutured to the edges of the chest wall defect using 0 Prolene in a simple continuous suture pattern.

The pectoral muscle was undermined, preserving its cranial and caudal insertions, to create a bipedicle flap. The bipedicle pectoral muscle flap was then pulled dorsally to cover the ventral aspect of the mesh.

The pectoral muscle was undermined, preserving its cranial and caudal insertions, to create a bipedicle flap. The bipedicle pectoral muscle flap was then pulled dorsally to cover the ventral aspect of the mesh.

The latissimus dorsi muscle was then transposed into the chest wall defect and sutured over the mesh to the cranial and caudal aspect of the defect and ventrally to the pectoral muscle flap.

Postoperative specimen image of the resected mass, a completely excised, grade I chondrosarcoma. The median survival time for dogs with primary rib chondrosarcoma varies from 1080 days to >3820 days. Unlike appendicular chondrosarcomas, histologic grade is not prognostic. The tumor-related mortality rate varies from 9% to 25%.

Postoperative specimen image of the resected mass, a completely excised, grade I chondrosarcoma. The median survival time for dogs with primary rib chondrosarcoma varies from 1080 days to >3820 days. Unlike appendicular chondrosarcomas, histologic grade is not prognostic. The tumor-related mortality rate varies from 9% to 25%.

Wide Trichoblastoma Resection and Local Advancement Flap Reconstruction

Signalment: 10-year-old, FS Labrador retriever

History:

Suspected local tumor recurrence following incomplete histologic excision of a benign trichoblastoma dorsal to the left upper eyelid.

Physical exam findings:

• 31.7 mm x 39.1 mm pedunculated and ulcerated cutaneous mass arising from the dorsal aspect of the left upper eyelid

• Left corneal opacity, stained negative

Diagnostic and clinical staging tests:

• CBC: mild anemia

• Serum biochemistry: no abnormalities

• Fine-needle aspirate: suspected trichoblastoma

Notes:

While I thought that this was most likely a local recurrence based on the history and location of this mass, we did also discuss the possibility of a malignant tumor because it is rare to see local tumor recurrence of a benign tumor, even following incomplete histologic excision, and the time interval since the first surgery (2 months), growth rate of the tumor, and appearance of the tumor (ulcerated) were all more consistent with a more aggressively behaving tumor.

Treatment:

Wide surgical resection with 2 cm lateral margins and temporal muscle fascia for deep margins, followed by reconstruction using a local advancement flap. The surgical defect could have been closed primarily but this would have resulted in distortion of the upper eyelid and possibly contributed to worsening keratitis. The advancement flap was advanced parallel to the eyelid to avoid distortion of the eyelid and maintain eyelid function.

Outcome:

• Benign trichoblastoma with complete histologic excision (narrowest lateral margins 13.0 mm)

• Mild surgical site infection, resolved with culture-directed antibiotics

Video link: https://www.youtube.com/watch?v=BhMrMKSpLtI&t=1506s

Tags: #trichoblastoma #reconstruction #advancementflap

Appearance of the suspected locally recurrent trichoblastoma immediately before surgery.

The mass was resected with 2 cm lateral margins and temporal muscle fascia (pictured) for deep margins.

The defect following wide resection of the mass. This could have been closed primarily, but this would have resulted in the upper eyelid being pulled dorsally and possibly preventing full closure of the eyelid, thus predisposing to keratonjunctivitis sicca and corneal ulceration. As a result, we planned on reconstructing this defect with a local advancement flap from the lateral face, parallel to the upper eyelid.

The width of the advancement flap is equal to the width of the defect, and the length was extended so that the flap could be advanced into the defect with minimal tension.

The advancement flap was undermined, preserving the subdermal plexus. This is a random pattern or subdermal plexus flap and the blood supply to the flap is dependent on preservation of the subdermal plexus.

The local flap was advanced into the defect.

Tag sutures were used on the corners of the advancement flap to maintain alignment of the flap while suturing it in place.

The advancement flap was secured in two layers, a subcutaneous layer using 3-0 Monocryl in a simple continuous suture pattern.

The advancement flap was secured in two layers, with skin sutures in the external layer consisting of 3-0 Nylon cruciate sutures on the leading edge of the advancement flap where there was the greatest potential for tension, and continuous Ford interlocking suture patterns along the rostral and caudal aspects of the flap where there was minimal tension.

The dog did have a surgical site infection and this quickly resolved following treatment with culture-directed antibiotics. This is the appearance of the advancement flap at suture removal 14 days postoperatively.

The dog did have a surgical site infection and this quickly resolved following treatment with culture-directed antibiotics. This is the appearance of the advancement flap at suture removal 14 days postoperatively.

Reverse Saphenous Conduit Flap for Resconstruction following Wide Resection of a Soft Tissue Sarcoma

Signalment: 11.5-year-old, MN German shepherd

History:

This dog was another tertiary referral after consulting with two surgeons and medical oncologists at two specialty hospitals in Toronto. He first presented to his family veterinarian 3 months beforehand with a12-month history of a slowly growing mass, now measuring 5 cm, ulcerated mass on the dorsal aspect of his left metatarsal region. A thorough workup was done (see below for results), but the dog had also developed a left pelvic limb lameness.

Physical exam findings:

• 45.8 mm x 48.2 mm ulcerated cutaneous mass on the dorsal aspect of the left metatarsal region; relatively mobile with no palpable invasion into deeper tissues of the metatarsal region

• Non-weight bearing left pelvic limb lameness with reluctance and pain on extension of the left hip

Diagnostic and clinical staging tests:

• CBC: no significant abnormalities

• Serum biochemistry: no significant abnormalities

• Three-view thoracic radiographs: no evidence of metastasis

• Biopsy: soft tissue sarcoma, grade I

• CT scan: L7-S1 intervertebral disc disease with formational impingement on the left side

Notes:

The dog presented to me with a non-weight bearing lameness on the same limb as his soft tissue sarcoma (STS). This is always a concern for me as it raises the possibility that the STS is invasive into deeper structures and causing the lameness. In such cases, the better option is often partial or full limb amputation. In this dog, however, the lameness was more consistent with lumbrosacral disease rather than an invasive STS. As such, a limb amputation would definitely not be the best option for the dog, in fact it would be the worst option for the dog. So a CT was done which confirmed the diagnosis of lumbrosacral disease due to asymmetric, chronic intervertebral disc disease at L7-S1. While waiting for the CT scan, he was started on Metacam and his lameness resolved, which was obviously a good sign as well.

We discussed the different options for management of his STS. Wide resection was recommended as marginal resection would still result in the need to reconstruct the wound; if the wound needs to reconstructed regardless, then it is best to do a wide resection to increase the chance of a complete histologic excision and decrease the risks of contaminating the defect and any reconstructive effort to reconstruct the defect. These options included second intention healing, singe-session resection and reconstruction with a reverse saphenous conduit flap, staged resection and reconstruction with a free-meshed skin graft, and staged reconstruction with a direct distant hinge flap. The latter was ruled out because of his lumbrosacral disease (although I do prefer this to free-meshed skin grafts), and the single-session reconstruction was preferred because the owners were from 5 hours away.

Treatment:

Wide resection of the STS, including digit extensor tendons for deep margins (yes, this is well tolerated!), and reconstruction of the defect with a reverse saphenous conduit flap. In addition, he received an epidural injection of methylprednisolone acetate to treat his lumbrosacral disease.

Outcome:

• Soft tissue sarcoma, grade II; complete histologic excision with 7.9 mm and 4.9 mm histologic tumor-free lateral and deep margins

• Distal flap incisional dehiscence followed 2 days later by complete flap necrosis and failure, possibly secondary to a bandage placed to manage the incisional dehiscence

• Acute and rapid lumbrosacral disease deterioration with non-ambulatory paraparesis and urinary incontinence

• Euthanasia 12 days postoperatively :(

Notes:

The grade shift between preoperative biopsy and definitive histopathology is not uncommon. In one study, 39% of dogs had a different histologic grade on their definitive histopathology compared to their preoperative biopsy, usually a grade higher than the biopsy.

I suspect that this dog’s flap necrosis started as a result of the bandage strangulating the median saphenous vein and caudal saphenous artery at the tibiotarsal joint. Prior to this, the flap showed no signs of vascular compromise with no bruising or necrosis. The bandage was necessary and it was just an unfortunate series of events.

I have not seen a dog with lumbrosacral disease deteriorate so rapidly before, and this was the ultimate reason for the owners electing euthanasia. We could have debrided the necrotic flap and managed the wound with second intention healing or a free-meshed skin graft; however, his lumbrosacral disease would have required a dorsal laminectomy with distraction-fusion, and this, combined with managing his wound, was a lot to put an old dog through.

Video link: https://www.youtube.com/watch?v=LYq6AscmM10

Tags: #STS #softtissuesarcoma #reconstruction #reversesaphenousconduitflap #complications #IVDD #LSdisease

The STS on the dorsal aspect of the left metatarsals with the borders of the reverse saphenous conduit flap marked with a sterile marker pen. The base of the flap is the medial malleolus, the caudal border is along the caudal aspect of and parallel to the tibia, the cranial border is along the cranial aspect of and parallel to the tibia, and the proximal border, in this dog, connected the cranial and caudal borders immediately distal to the level of the patella.

The flap was raised before resection of the STS with incisions along the proximal, cranial, and caudal borders of the flap. The saphenous artery and vein were sealed and transected with a LigaSure near to the proximal aspect of the flap, and the flap was undermined deep to the subcutaneous tissue.

During dissection, a segment of the medial gastrocnemius fascia was raised with the flap to protect the median saphenous vein and caudal saphenous artery.

The reverse saphenous conduit flap was raised in a proximal to distal direction, preserving the tibial nerve caudally.

The flap donor site was then closed prior to wide resection of the STS to minimize the risk of contaminating the flap donor site with tumor cells.

Appearance of the raised reverse saphenous conduit flap following closure of the donor site.

A bridging incision was then done to connect the flap donor site and the planned defect following resection of the STS.

The STS was resected with 1.5 cm lateral margins.

Deep margins were extended to the metatarsal bones, including the digit extensor tendons and joint capsule of some of the metatarsophalangeal joints.

The reverse saphenous conduit flap was then transposed into the defect.

After transposition, the reverse saphenous conduit flap was secured into the defect in two layers, a 3-0 Monocryl simple continuous suture pattern in the subcutaneous layer and staples in the skin.

Appearance on postoperative day 1. There is mild bruising but the flap was warm throughout. Note the position of the proximal flap with the hock flexed. I think this, in combination with the bandage, may have played a role in strangulating the median saphenous vein and caudal saphenous artery at the tibiotarsal joint later in the postoperative period.

Two days postoperatively, the distal aspect of the flap had incisional dehiscence. There is some deeper bruising along the distal aspect of the flap.

Four days postoperatively, there is some necrosis of the distal aspect of the flap (arrows) but the remainder of the flap appears relatively healthy with no evidence of impending doom, which I would usually expect to see by this stage with typical distal flap necrosis.

This is the more concerning image because there is tissue necrosis at the junction of the distal aspect of the flap donor site and the proximal aspect of the bridging incision.

The distal aspect of the flap was debrided and closed primarily. This was closed with as little tension as possible because tension at the distal aspect of the flap can reduce partial pressures of oxygen and lead to further flap necrosis.

The appearance of the flap three days later, seven days postoperatively. Very, very sad. This is not a typical progression or timing for flap necrosis, so I suspect the bandage may have exacerbated pressure at the hock joint when in flexion and resulted in compression of the the median saphenous vein and caudal saphenous artery at the level of the tibiotarsal joint.

Appearance of the flap 10 days after surgery.

Incisivectomy in a Dog with an Acanthomatous Ameloblastoma

Signalment: 7-year-old, FS Australian shepherd criss

History:

This dog presented to her family veterinarian with a rapidly growing rostral maxillary mass. Blood work was done and a biopsy was consistent with an acanthomatous ameloblastoma (AA).

Physical exam findings:

The only abnormality was a raised mucosal covered mass extending from 102 to 203.

Diagnostic and clinical staging tests:

• CBC: no abnormalities

• Serum biochemistry: increased SDMA with normal BUN and creatinine

• Urinalysis: no abnormalities

• Biopsy: acanthomatous ameloblastoma

Treatment:

The three treatment options for dogs with AA are surgery, radiation therapy, and intralesional bleomycin. Of these, surgery is usually recommended because it is typically quicker and cheaper and more likely to achieve tumor control. Because of the location of the AA in this dog, the AA was able to be resected with 1 cm caudal margins using a biradial (TPLO) saw to preserve the canine teeth. This procedure is called an incisivectomy.

Outcome:

• Acanthomatous ameloblastoma excised with complete histologic margins with the narrowest lateral margin measuring 2.0 mm and the narrowest caudal histologic tumor free margin measuring 4.4 mm.

• Minor wound dehiscence which healed by second intention.

• This surgery should be curative for this dog as AAs are benign tumors and local recurrence is rare, especially following complete histologic excision.

Video link: https://www.youtube.com/watch?v=1L8E27cYyIc&t=4s

Tags: #CAA #acanthomatousameloblastoma #incisivectomy #maxillectomy

Immediate preoperative image of the acanthomatous ameloblastoma, a benign but invasive oral tumor, arising from the upper incisor region in a dog.

Immediate preoperative image of the acanthomatous ameloblastoma, a benign but invasive oral tumor, arising from the upper incisor region in a dog.

The gingiva mucosa is incised with a number 10 or 15 scalpel blade and then reflected caudally to expose the dorsal aspect of the planned osteotomy.

A 27 mm biradial saw was then pressed against the palatine mucoperiosteum to create an imprint in the mucoperiosteum, and an incision was made through the mucoperiosteum along this imprint. The mucoperiosteum was then reflected caudally with a periosteal elevator, and the incisivectomy was then performed with a 27 mm biradial (TPLO) saw. This is what these saw blades were really designed for!

Following the incisivectomy, the transected roots of the incisor teeth were extracted.

Intraoperative image showing all of the retained tooth roots have been removed.

The mucosal incision was closed in a single layer of 3-0 PDS suture material in a cruciate suture pattern.

Postoperative specimen image with caudal margins inked. This was histologically confirmed as a completely excised (4.4 mm caudal margins), benign acanthomatous ameloblastoma.

Postoperative appearance 1 day after surgery. There is a very mild droop of the rostral nose.

Radical Mandibulectomy in a Cat with a Mandibular Squamous Cell Carcinoma

Signalment: 15.5-year-old, FS domestic shorthair cat

History:

This cat presented to her family veterinarian with a mandibular mass, and was then referred to a local specialty hospital. She had a previous history of small T-cell intestinal lymphoma, chronic pancreatitis, and progressive azotemia. Her small T-cell intestinal lymphoma was previously treated with chlorambucil and prednisolone but the chlorambucil was discontinued 9 months prior to the development of her oral mass. Fine-needle aspirate cytology of the mandibular mass was consistent with an osteosarcoma, which carries a very good prognosis in cats following surgery alone. She was initially treated with Palladia and one fraction of palliative radiation before the owner contacted me regarding the possibility of mandibulectomy and reconstruction with a patient-specific, 3D printed implant.

A CT scan was done at the local specialty hospital which showed a non-metastatic left mandibular mass. Resection was definitely possible based on this CT scan but the amount of bone stock available on the caudal left mandible was limited, making reconstruction with a patient-specific, 3D printed implant challenging. I worked with Laurent Lacombe at NXMed (https://nxmed.ca/home) to design a composite implant that would meet the challenging needs to reconstruct this defect, including a biocompatible PEKK implant to reconstruct the mandible, with the rostral mandible shortened by 15 mm, and a titanium plate to fix to the PEKK implant and residual mandibular bone.

Physical exam findings:

The cat was referred from New Jersey and presented to me at Capital City Specialty & Emergency Animal Hospital after the patient-specific implant had been manufactured and delivered to me, about 3 weeks after her CT scan. On examination, she had a large left mandibular mass extending to the rostral midline and caudally along the left mandible., much further caudally than on her CT scan. Unfortunately, her tumor had grown in the period between her CT scan and surgery, much more so than anticipated (as I had added an additional 1 cm to the caudal margins to account for this potential growth). I discussed the possibility of not being able to reconstruct her mandible with her owner and her owner decided to proceed with surgery with the plans of reconstructing if possible, modifying the reconstruction if different to the original plan pending the amount of available bone remaining, or proceeding with a radical mandibulectomy if reconstruction was not possible because of the caudal growth of the tumor along the left mandible.

Diagnostic and clinical staging tests:

• Fine-needle aspirate: osteosarcoma

• CBC: moderate anemia (PCV 24.5%) with mild leukocytosis and neutrophilia

• Serum biochemistry: increased BUN (15.5 mmol/L) with high normal creatinine (137 umol/L)

• Abdominal ultrasound: borderline increases in the size of the right kidney and pancreas

• CT scan: left mandibular mass and no evidence of pulmonary metastasis

• Three-view thoracic radiographs (immediately prior to surgery): no evidence of lung metastasis but a moderate diffuse interstitial pattern and cardiomegaly (cat had a grade III/VI heart murmur). Possibilities suggested for this interstitial pattern included pulmonary edema secondary to left-sided heart failure (unlikely because of she had no respiratory distress), an infiltrative neoplastic process such as lymphoma, or, less likely, pulmonary hemorrhage, pulmonary fibrosis, or interstitial pneumonia.

Treatment:

After much debate about positioning, she was positioned in dorsal recumbency. The standard intraoral approach was made for a mandibulectomy. A left commissurotomy was done to assess the caudal extent of the tumor. Unfortunately, her tumor extended to within millimetres of the caudal aspect of the vertical ramus. As a result, reconstruction was not possible and we had to perform a radical mandibulectomy instead. From this approach, her temporomandibular joint was disarticulated, an osteotomy of the right mid-mandible was performed with a sagittal saw (1 cm caudal to the caudal extent of the tumor on the right side), and then the mandibular segment was reflected laterally to seal and transect the mandibular alveolar artery and other soft tissues to complete the radical mandibulectomy. The mucosa was then closed, excessive skin on the ventral chin was resected, and the skin was then closed. An esophagostomy tube was placed because supplemental tube feeding is often required in the initial weeks following mandibulectomy in cats.

Outcome:

• Grade II mandibular squamous cell carcinoma (SCC) with complete histologic (R0) excision, 3.3 mm histologic tumor-free margins on the lingual aspect, 2.6 mm ventrally, and caudal margins of 10 mm on the left side and 20 mm on the right side.

• Died 6 days postoperatively of unknown causes in her sleep. She had no preceding signs of illness. Unfortunately for this owner, this cat was one of five in their household, two others of which died of respiratory-related illnesses in the same week as this cat with the other two being hospitalized with respiratory disease but later recovering.

Video link: https://lnkd.in/dWwetQMH

Notes:

While I am not sure if it would have made a difference for this owner, this cat was diagnosed cytologically with an osteosarcoma preoperatively but a SCC on definitive histopathology. Mandibular osteosarcomas have a more benign biological behaviour in cats whereas SCCs are more aggressive locally, which would explain the rapid tumor growth in the 3 weeks between her CT scan and surgery.

Tumor growth during the design and manufacture process is a known challenge when using patient-specific implants for reconstructing osseous defects following tumor resection. In one study of dogs treated with limb-sparing surgery using patient-specific implants, radiation therapy and intravenous chemotherapy were ineffective in limiting tumor growth during the period required for design and manufacture of the implant, with only regional intra-arterial chemotherapy being effective. Other options include modifying the implant design to account for estimated tumor growth (which I did in this case) or staging the resection and reconstruction so that the tumor is resected and then a CT is done immediately postoperatively and the defect is reconstructed after the implant has been designed, manufactured, and delivered. This latter option is acceptable for mandibular reconstructions but not for surgeries like limb salvage.

Despite the aggressiveness of this surgery, cats can do well following radical mandibuelctomy. In one study of eight cats treated with radical mandibulectomy, th mean survival time was 712 days and six of these cats returned to voluntary eating.

Tags: #SCC #FOSCC #mandibulectomy #patientspecifcimplant #PEKK

Reconstructed CT image with planned reconstruction of the mandibular defect using a composite PEKK implant and 2.0 mm titanium plate.

3D-printed model of the mandible of this cat for surgical planning.

3D-printed model of the mandible of this cat with the cutting guide in place.

The finished product with the PEKK implant to reconstruct the mandible and the 2.0 mm titanium plate, designed to accommodate 2.0 mm Arthrex screws, to fix to the implant and residual mandibular bone.

The gross appearance of the mandibular mass at surgery.

The gingival mucosa is carefully incised with a number 15 scalpel blade, avoiding inadvertent compromise of the tumor capsule.

The skin of the ventral chin is then reflected off the tumor with blunt dissection using Metzenbaum or iris scissors.

A commissurotomy was then performed with Mayo scissors. I started this incision slightly ventral to the caudal commissure to preserve the buccal mucosa for closure.

The commissurotomy was continued deeply and caudally with a vessel sealing device (LigaSure).

Once the commissurotomy was extended caudally, the caudal extent of the tumor could be visualized. Unfortunately, it had extended too far caudally to be able to preserve any bone for fixation of the titanium plate. As a result, our plans to reconstruct the mandible had to be abandoned and we resorted to treating this cat with a radical mandibulectomy.

The temporomandibular joint was disarticulated.

An osteotomy of the right mandible was performed with a sagittal saw 2 cm caudal to the caudal extent of the tumor on this side.

The completed right-sided mandibular osteotomy following cauterization of the mandibular alveolar vessels within the mandibular canal.

The mandibular segment was then reflected laterally to expose the left mandibular alveolar vessels entering the mandibular canal. These were sealed and transected with a LigaSure.

The surgical field following completion of the radical mandibulectomy.

The mucosa was closed in a combination of cruciate and simple continuous suture patterns using 4-0 Monocryl.

The completed mucosal closure.

Because of the extent of the resection, there was excessive ventral chin skin.

This excessive skin was excised with Mayo scissors.

This is the defect following excision of the excessive ventral chin skin.

This was closed in a single layer of 4-0 Monocryl cruciate sutures.

Appearance following closure of the radical mandibulectomy in this cat.

Appearance following closure of the radical mandibulectomy in this cat.

An esophagostomy (e)-tube was then placed. Forceps were inserted from the oral cavity and into the esophagus to tent the skin on the left lateral neck.

A stab incision is then performed over the tips of the forceps, the forceps are punched through the wall of the esophagus and through the stab incision, and the forceps are used to grasp the distal aspect of the e-tube.

A stab incision is then performed over the tips of the forceps, the forceps are punched through the wall of the esophagus and through the stab incision, and the forceps are used to grasp the distal aspect of the e-tube.

The e-tube is then pulled out through the oral cavity.

The e-tube is then retroflexed into the esophagus and extended down to a premeasured level at approximately the level of the heart base.

Appearance following closure of the radical mandibulectomy and placement of the e-tube in this cat.

Appearance following closure of the radical mandibulectomy and placement of the e-tube in this cat.

Gross specimen image of the mandibular mass. This was diagnosed as a completed excised, moderately differentiated SCC.

Rectal Adenocarcinoma Resected via a Rectal Eversion and Submucosal Resection Technique

Signalment: 11-year-old, MN Siberian husky cross

History:

This dog presented to our ER service with a 6-week history of bloody diarrhea and intermittent bleeding from his rectum. On rectal exam, a mass was palpable on the dorsal aspect of the rectum. There were no abnormalities on either APOCUS or TPOCUS.

Physical exam findings:

9.6 mm x 9.6 mm subcutaneous mass on the dorsomedial aspect of the left carpus. No other abnormalities noted.

Diagnostic and clinical staging tests:

• Fine-needle aspirate: poorly exfoliative mast cell tumor (MCT)

• CBC: mild anemia (PCV 35%)

• Serum biochemistry: increased ALT (250 U/L) and ALP (269 U/L)

• Three-view thoracic radiographs: no evidence of lung metastasis

• Abdominal and thoracic CT scan: focal enteropathy in the descending colon to rectum, no evidence of intra-abdominal or intra-thoracic metastasis, normal thorax, and several non-specific and insignificant findings in the abdomen

Treatment:

Following induction of anesthesia, the dog was positioned in sternal recumbency and the tail was elevated. The rectal mucosa was everted with five 3-0 PDS stay sutures. Once the mass was exteriorized, a subcmucosal resection was performed with approximately 5 mm lateral margins. The rectal mucosa was then sutured with a single layer of 3-0 Monocryl in a simple continuous suture pattern.

Outcome:

• Grade I rectal adenocarcinoma with complete histologic (R0) excision, 4.7 mm histologic tumor-free lateral margins and 3.0 mm deep margins

• No evidence of local recurrence 4 months postoperatively

Notes:

There are three different surgical approaches for management of rectal carcinomas: rectal pull-through, rectal mass resection via a dorsal inverted U-approach, or rectal eversion and submucosal resection. Rectal resection and anastomosis via a dorsal inverted U-approach is only indicated for focal lesions in the region of the dorsal rectum. Rectal pull-through procedures are associated with a high risk of fecal incontinence and rectal stricture formation (see https://pubmed.ncbi.nlm.nih.gov/25181273/). The trend is to be more conservative with resection of rectal masses, typically through a rectal eversion (or transanal) and submucosal resection approach. The results for this approach are surprisingly good despite being more conservative. In one study of 93 dogs treated with the approach, the local recurrence rate was 21% and the majority of these were treated with repeat submucosal resection. For dogs with rectal carcinomas, the median survival time was not reached with 1-, 2-, and 5-year survival rates of 95%, 89%, and 73% respectively.

Tags: #rectalcarcinoma #transanal #rectaleversion #submucosalresection

The rectal mass was exteriorized by progressively everting the rectal mucosa using 3-0 PDS stay sutures.

Once exteriorized, an incision was made into the rectal mucosa and the rectal mucosa was undermined deep to the rectal mass. The mass was then resected by incising around the mass and the rectal mucosa with Metzenbaum scissors with approximately 5 mm lateral margins.

Once resected, bleeding was controlled with electrosurgery and then the rectal mucosal incision was closed in a single layer with a simple continuous suture pattern using 3-0 Monocryl.

The completed closure of the rectal mucosal defect.

The appearance following release of the stay sutures. The discharge instructions for these cases are one of the easiest to follow because there is no exercise restriction and no sutures to remove!

Subcutaneous MCT with Transposition Flap Reconstruction

Signalment: 3.5-year-old, FS Potcake

History:

New mass was noted on the dorsal aspect of the left forepaw, present for 1 week.

Physical exam findings:

9.6 mm x 9.6 mm subcutaneous mass on the dorsomedial aspect of the left carpus. No other abnormalities noted.

Diagnostic and clinical staging tests:

• Fine-needle aspirate: poorly exfoliative mast cell tumor (MCT)

• CBC: no significant abnormalities

• Serum biochemistry: no significant abnormalities

Treatment:

Sentinel lymph node (SLN) mapping was performed prior to surgery using 0.5 ml Omnipaque in each of four peritumoral quadrants followed by radiographs at 0, 1, and 3 minutes. This showed simultaneous contrast enhancement of both the ipsilateral superficial cervical (prescapular) and axillary lymph nodes.

A hook needle was inserted into the left axillary lymph node under ultrasound guidance to assist in intraoperative identification of the lymph node.

Intraoperative SLN mapping was performed with 0.5 ml methylene blue in each of four peritumoral quadrants. A standard approach was used to resect the superficial cervical lymph node. An incision was performed adjacent to the hook needle and this incision was continued deeply to identify and excise the axillary lymph node.

The subcutaneous MCT was resected with 10 mm lateral margins and fascia for deep margins. Primary closure was not possible and the defect was reconstructed with a random subdermal plexus transposition flap.

Outcome:

• Low grade II MCT with complete histologic (R0) excision, 4.4 mm histologic tumor-free lateral margins and 3.6 mm deep margins

• Local flap failure, possibly because of a bandage-related complication. The flap had partial incisional dehiscence and a surgical site infection at postoperative day 11 but was the flap was intact with no necrosis. The flap still appeared 100% viable on postoperative days 12 and 13; but on postoperative day 14, 100% of the flap had become necrotic. This is a very late time period for a flap to fail and it is unusual for the entire flap to fail, so I suspect that the infection and/or the bandage may have contributed to flap failure in this case.

• Complete healing by day 43 with second intention.

Tags: #MCT #SLN #SLNmapping #localflap #transpositionflap #reconstruction #secondintentionhealing #complication

Preoperative sentinel lymph node (SLN) mapping showing afferent lymphatic drainage (arrow heads) towards two different but synchronous SLNs, the superficial cervical (or prescapular) and axillary lymph nodes

Preoperative SLN mapping show two synchronous SLNs, which is not very common compared to a single SLN, the ipsilateral superficial cervical and axillary lymph nodes (arrows).

Dr. Gower, one of our board-certified medical oncologists, using an ultrasound intraoperatively to place a hook wire adjacent to the axillary lymph node to aide in identification of the lymph node for excision. (Normal sized axillary lymph nodes are difficult to find!).

Intraoperative SLN mapping was then done with sterile methylene blue injected peritumorally in four-quadrants around the MCT.

The superficial cervical lymph node was excised using a standard approach. Blue discolouration of the lymph node confirms that this is a SLN, corroborating the preoperative SLN mapping findings.

An incision was then performed adjacent to the hook needle and dissection was continued deeply along the hook needle until the axillary lymph node was identified.

Once identified, the axillary lymph node was extirpated using a LigaSure.

Following extirpation of both SLNs, the MCT was resected with 10 mm lateral skin margins and wider subcutaneous tissue margins and one uninvolved fascial layer for deep margins. In these cases, it is more important, at least in my opinion, to get margins in the subcutaneous tissue because this is the anatomical layer from which this tumur is arising, not the skin.

Note the degree of blue discolouration at the surgery site as a result of the intraoperative SLN mapping with methylene blue. This is normal. It is important to mark your lateral margins with a sterile marker pen prior to doing intraoperative SLN mapping so that your surgical approach is not compromised by the blue discolouration in the surgical field.

Because the wound could not be closed primarily, I planned to use a transposition flap from the dorsal aspect of the antebrachium. I recently lectured at the VetEducation Masterclass in Valencia and one of my colleagues and co-lecturers, Dr. Laurent Findji from AURA Veterinary in the UK, showed us this flap. This wound was perfect for reconstruction with this flap. In this photo, you can see me elevating the skin on the dorsal aspect of the antebrachium, demonstrating how much available skin there is this region.

An incision was performed medially and laterally along the elevated skin, with the length of the flap determined by the size of the wound defect.

The flap was then transposed 180 degrees into the defect.

Once transposed into the defect, the flap was sutured with a two layer closure.

Appearance of the flap on postoperative day 1. The blue discolouration of the flap was residual staining from the methylene blue. The flap remained warm and viable despite this appearance.

The flap developed acute and complete necrosis on postoperative day 14. The wound was initially managed with wet-to-dry bandages. This is the appearance of the wound on day 2 of second-intention healing, with a healthy granulation tissue bed developing.

Day 9 of second-intention healing. The wound was initially managed with daily bandage changes using a non-adherent Telfa pad as the contact layer. The wound has undergone some contraction but minimal epithelialization at this stage.

Day 17 of second-intention healing. The rate of contraction is beginning to accelerate as the wound is visibly smaller.

Day 23 of second-intention healing. The wound is contracting nicely. I forget the actual timing but we have likely changed to bandage changes every 2 days by this time and will soon start using Dermagel, a hydrogel, as the contact layer.

Day 30 of second-intention healing. The wound is contracting beautifully. It is interesting how some wound will initially be slow to start healing but then they go through a rapid phase of healing, such as in this dog.

Day 37 of second-intention healing. Almost there. By this stage, the owner is doing bandage changes every 4 days and continuing with DermaGel as the contact layer. The wound is likely epithelializing under the scabs that have formed over the incision in areas.

Day 43 of second-intention healing. All healed. Yay!

A few points:

• This was a subcutaneous MCT (despite being read out using a grading scheme only validated for cutaneous MCTs). Most subcutaneous MCTs have a more benign biological behaviour compared to cutaneous MCTs. In one study of 306 dogs with subcutaneous MCTs, the metastatic rate was only 4% and the local recurrence rate was only 8% (despite 56% of these MCTs being incompletely excised with a 2% and 12% local recurrence rate for completely and incompletely excised MCTs, respectively). The median survival time was not reached in this study with estimated 1-, 2-, and 5-year survival times of 93%, 92%, and 86%, respectively, with surgery alone. Decreased survival times was reported with increased mitotic rate, infiltrative growth pattern, and presence of multinucleated cells. Because of the less aggressive nature of many subcutaneous MCTs, surgical resection can be more conservative with a good chance of success.

• The complication rate following reconstruction with a subnormal plexus flap, such as this transposition flap, is 51%.

• Second-intention healing can be used as a rescue option for failed reconstructive surgery or can be used as a first-line option to manage an open wound following a tumor resection instead of using a reconstruction option.

• Second-intention healing is a labour intensive option. Owners are typically shown how to bandage changes, as was the case with this dog. I encourage owners to email me after each bandage change with a photo of the wound and an assessment of the wound, as well as how they are going with the bandage changes. This allows me to provide information on when the contact layer should be changed and when the frequency of bandage changes can be extended. The owners and I become quite familiar by the end of this process! This dog’s owners did a fantastic job in bandaging and managing her wound, as evidenced by a completely healed wound in less than 6 weeks.