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Contact Information

Phone: 919.513.6690
Fax:  919.513.6669

Hours: Monday-Friday, 8AM-5PM
Regular appointments: 
Drop-offs:     7:30AM-8:30AM
Discharges:   4PM-6PM

The Oncology service is a referral-only service. Once the primary veterinarian calls and sets up the referral, the owner may call and arrange an appointment. If the patient has been seen by our service recently, owners may call Oncology directly to set up an appointment.

General Information

The Terry Center

red Cross Cadeceus

Emergency Service

Main Number: 919.513.6500
Small Animal Emergency: 919.513.6911
Large Animal Emergency: 919.513.6630
Monday-Thursday 5PM-8AM
Friday 5PM-Monday 8AM

Open 24 hours on legal holidays.
No appointment needed.


Mast Cell Tumors in Dogs

What are Mast Cell Tumors?

Mast cell tumors are one of the most common skin tumors in dogs. They are highly variable in appearance. We recommend that all masses be evaluated with fine needle aspiration cytology which can readily diagnose most mast cell tumors as well as a variety of other tumors. Once a mast cell tumor is identified, we recommend that a biopsy be performed to confirm the diagnosis and determine the tumor "grade." The specific behavior, treatment recommendations and prognosis correlate with the grade of the tumor.

Tumor Grades/Diagnostic Testing

MCT cytology

Grade I mast cell tumors are minimally invasive and spread to other places in the body (called metastasis) is not expected. Wide surgical excision should be curative.

Grade II mast cell tumors are invasive into adjacent tissues, although again, metastasis is uncommon. Diagnostic tests are recommended to ensure there is no obvious evidence of spread to other places in the body. These tests include:

Wide and complete surgical excision is the treatment of choice. If this is not possible, the combination of surgery (to remove obvious gross disease) followed by radiation therapy (to destroy residual microscopic disease) is very effective. This combination is associated with a 95% chance of 1-year tumor control and an approximately 85-95% chance of 2-5 year control.

Grade III mast cell tumors are locally invasive and differ from grade II tumors in having a moderate-high rate of metastasis. Diagnostic tests are recommended to ensure there is no obvious evidence of spread to other places in the body. These tests include:


Treatment ideally consists of local therapy as described for grade II mast cell tumors combined with systemic chemotherapy aimed at delaying or preventing the onset of metastatic disease. Our current protocol involves a combination of prednisone, vinblastine, and CCNU, the three drugs with demonstrated effectiveness against mast cell tumors. Chemotherapy can also be used alone if surgery and radiation therapy are not performed. Mast cells contain and can release numerous granules (e.g. histamine) and when present in high concentrations, these substances can become irritating to the stomach and other organs. To protect the body from these granules, we recommend that dogs with grade III mast cell tumors be treated continuously with both H1 (diphenhydramine) and H2 (cimetidine, famotidine, or ranitidine) receptor antagonists.

Selected References