Ask a UW Veterinarian: Tricky Tumors



The question below was featured in the Winter 2016-17 issue of On Call, the magazine for friends of the UW School of Veterinary Medicine. This issue’s expert response comes from Ruthanne Chun, a board-certified veterinary medical oncologist and director of UW Veterinary Care.

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What is the incidence of mast cell tumors in a dog after successful chemotherapy treatment? My dog, Sumo, was treated at UW Veterinary Care and has been in remission for three years, but we recently found three small tumors on him. The tumors were removed this week by our local veterinarian, and we are waiting on the pathology report.
–Kathy Trudelle, Sauk Village, Ill.

Mast cell tumors are one of the most difficult to predict in terms of response to therapy, recurrence, and cure rate. Factors that go into determining treatment recommendations include location and rate of growth of the tumors, number of sites affected, and the microscopic appearance of the tumor. Since your dog was treated with chemotherapy, it is likely that the oncologists were concerned that those particular mast cell tumors were more aggressive and had the potential to recur. However, it is unusual that your dog had three years of remission before new tumors occurred. Fingers crossed that these are not mast cell tumors and that they are some other benign growth.

Editor’s note: Prior to going to press, we received good news that the growths on Sumo’s skin were not mast cell tumors, rather, they were benign dermal fibrosis and were removed successfully.

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