renal tumors

BACKGROUND

Renal tumors are uncommon in cats and dogs. Clinical signs are usually non-specific and tumors can get very large before they are diagnosed. The vast majority of renal tumors are malignant with most having a moderate to high metastatic risk. Lymphoma is the most common renal tumor in cats. Renal carcinoma is the most common tumor of the canine kidney, but a variety of other tumors are also reported including transitional cell carcinomas, cystadenocarcinomas (in German Shepherd Dogs), various types of sarcomas (ie, hemangiosarcoma), and nephroblastomas.

DIAGNOSIS

Kidney tumors are diagnosed with urinalysis, blood tests, and imaging modalities such as radiographs, ultrasound (preferred), and CT scans. Ultrasound-guided fine-needle aspirates are recommended, particularly in cats, to differentiate lymphoma from other types of renal tumors.

CLINICAL STAGING

Chest radiographs or CT scans are done to check for metastasis to the lungs. An abdominal ultrasound is recommended to check for metastasis to the regional lymph nodes and liver. As nephrectomy (or surgical removal of the kidney) is the recommended treatment for all renal tumors other than lymphoma, the function of the normal kidney should be evaluated prior to surgery with blood tests, excretory urogram, or nuclear medicine (radiactive glomerular filtration scans).

TREATMENT

The recommended treatment for all renal tumors other than lymphoma is nephrectomy, which involves removal of the affected kidney and its ureter.

Lymphoma is treated with multiagent chemotherapy protocols. Because of the relatively high metastatic risk of malignant renal tumors, chemotherapy should also be considered for carcinomas, sarcomas and nephroblastomas. However, an effective protocol has not been identified in dogs and response rates in people with renal tumors is low. Immunotherapy is commonly used in the treatment of renal carcinoma in people but this has not been investigated in cats or dogs.

PROGNOSIS

The prognosis is fair for cats and dogs with renal tumors and is dependent on tumor type. The mean survival time for cats with renal lymphoma treated with chemotherapy is 408 days and this is significantly better for cats that are FeLV negative (mean survival time 610 days), mild renal dysfunction, and those with a complete response to chemotherapy.

The median survival time for dogs with surgically excised renal tumors is 16 months for carcinomas, 9 months for sarcomas, and 6 months for nephroblastomas. Individual survival times of greater than 25 months have been reported for dogs with nephroblastoma treated with surgery and chemotherapy. In 70 dogs with renal carcinomas treated with nephrectomy (2015), a number of poor prognostic factors for overall and disease-specific survival were identified on univariate analysis including hematuria and cachexia on presentation, mitotic index, nuclear size, nuclear pleomorphism, tumor differentiation, invasiveness, Fuhrman nuclear grade, and clear cell morphology. More importantly, on multivariate analysis, mitotic index was identified as an independent prognostic factor. The median survival times for dogs a mitotic index < 10, 10-30, and > 30 were 1,184 days, 452 days, and 187 days, respectively. In another study of 64 dogs with renal carcinoma treated with nephrectomy (2017), of which 42% were also treated with adjuvant chemotherapy, COX-2 expression, mitotic index, histologic type, vascular invasion, neoplastic invasiveness, and metastasis at diagnosis, which was diagnosed in 13% of dogs, were significantly associated with overall median survival time on univariate analysis. Independent prognostic factors on multivariate analysis included COX-2 score and mitotic index. The median survival times were 540 days and 120 days for dogs with a mitotic index < 30 and > 30, respectively. The median survival times were 1,176 days and 420 days for dogs with a COX-2 score < 3 and > 3, respectively.

Last updated on 20th May 2019