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Tumor Recurrence in Dogs

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Last Modified: June 28, 2006

Dear OncoLink "Ask The Experts,"

Ten weeks ago my 4 year old male golden retriever had a tumor removed from his paw. Biopsy stated benign subungual keratoacanthoma. Xray taken during surgery showed no bone involvement. The incision healed well, no infection or post-op problems. The tumor is growing back at the same place. Is this unusual? Could it be malignant?

Lili Duda, VMD, Section Editor of the OncoLink Veterinary Oncology Menu, responds:

Any tumor, whether benign or malignant, can recur if the tumor was not completely removed by the surgical procedure. A complete removal means not only the visible portion of the tumor, but also any roots or tendrils from the tumor that are growing or extending into the surrounding normal tissues. A complete biopsy report should describe the appearance of the tumor as well as the completeness of the surgical margins. If the surgeon sent only a representative sample of the tumor for biopsy, rather than the entire specimen, it is impossible for the pathologist to comment on the completeness of surgical removal.

The primary differences between benign and malignant tumors are that benign tumors do not metastasize (spread elsewhere in the body), and benign tumors tend to be more slowly growing and less invasive (i.e., less aggressive)than malignant tumors. If a biopsy report does not match the veterinarian's clinical impression of the tumor, or if the biospy report is equivocal, the veterinarian can talk to the pathologist who read the biopsy, and/or request a second opinion.