pancreatic tumors
BACKGROUND
Adenocarcinoma
Pancreatic tumors are uncommon in both cats and dogs. Pancreatic tumors are divided into exocrine and endocrine neoplasia. Exocrine pancreatic tumors are usually malignant adenocarcinomas. Diffuse involvement of the pancreas is common and they are often associated with obstruction of the common bile duct (causing jaundice). There is a very high risk of metastasis.
Insulinoma
Insulinomas arising from pancreatic islet cells are the most common endocrine pancreatic tumor in dogs. Insulinomas cause hypoglycemia (or low blood glucose). Hypoglycemia is responsible for the clinical signs seen in dogs with insulinomas, such as weakness, ataxia, collapse, and convulsions. Metastasis to the regional lymph nodes and liver is common.
DIAGNOSIS
An insulinoma is highly suspected when blood tests reveal simultaneous hypoglycemia and hyperinsulinemia (or high blood insulin). Ultrasonography is recommended for both diagnosis and clinical staging of cats and dogs with any type of pancreatic tumor. Insulinomas are often small and can be difficult to detect with ultrasonography. Other imaging modalities, such as endoscopic ultrasonography and nuclear scintigraphy, have been described for the diagnosis of insulinomas but are not widely available.
CLINICAL STAGING
An abdominal ultrasound is recommended to check for metastasis to the regional lymph nodes and liver. Chest radiographs or CT scans are done to check for metastasis to the lungs.
TREATMENT
Adenocarcinoma
Exocrine pancreatic adenocarcinomas are usually advanced by the time of diagnosis and, similar to the same disease in people, there is no known effective treatment. Surgical excision should be considered for localized, non-metastatic tumors. Palliative bypass surgery, such as cholecystoduodenostomy (or suturing the gall bladder to the small intestines), can provide relief of clinical signs caused by obstruction of the common bile duct.
Insulinoma
Partial pancreatectomy is recommended for dogs with non-metastatic insulinomas. The vast majority of insulinomas are small (< 1 cm) which can make identification of the tumor difficult. Intraoperative ultrasound or intravenous injection of methylene blue can assist with identification of insulinomas if they are not readily visible during surgery. The majority are solitary, but multiple and diffuse tumors are reported in up to 20% of dogs. Enlarged or metastatic lymph nodes should be excised if possible. Common complications include pancreatitis, persistent hypoglycemia because of inoperable or metastatic disease, and transient or permanent diabetes mellitus.
Medical management of hypoglycemia should be considered for dogs with metastatic insulinoma. This involves small and frequent meals high in protein and low in simple sugars, prednisone, and oral hyperglycemic drugs such as diazoxide or octreotides.
Chemotherapy using streptozotocin has been described in dogs with insulinoma.
PROGNOSIS
Adenocarcinoma
The prognosis for cats and dogs with exocrine pancreatic adenocarcinoma is grave because of local invasiveness and diffuse pancreatic involvement and frequent metastasis. Treatment is often not possible and the majority of animals are euthanased within 7 days of diagnosis.
Insulinoma
The prognosis for dogs with insulinoma is good to guarded and is dependent on clinical stage and treatment methods. The prognosis is significantly better for dogs without metastasis or metastasis to the regional lymph nodes compared to dogs with metastasis to the liver and other organs with a median survival time of 18 months compared to < 6 months. The median survival time for dogs treated conservatively is 74 days compared to 381 days for surgically-managed dogs. Partial pancreatectomy is preferred as the mean survival time of 17.9 months is significantly better than the 11.5 months reported following enucleation of the tumor. Lastly, persistent postoperative hypoglycemia is a poor prognostic sign with a median survival time of 90 days compared to 680 days for normoglycemic dogs.
To be updated