EQUINE MELANOMA: HARMLESS BUMP OR TIME BOMB?

Alyssa Davidson’s gray gelding, Goose, was 13 when she first noticed a dark growth on him. The North Carolina rider didn’t recall seeing the lump located on his penis before, but she couldn’t be sure it hadn’t been there all along. Could it be melanoma, she wondered? How worried should she be? Melanomas, a type of cancerous tumor, are common in gray horses. If one of these tumors popped up on your skin, you’d rush to the doctor—and rightly so since human melanomas are malignant and can quickly metastasize, spreading to distant sites in the body. But, says Chris Byron, DVM, “Melanomas in gray horses exhibit behavior that is quite different from melanomas in humans.” Gray-horse melanomas commonly grow slowly, if at all, for years. They may never metastasize. That doesn’t mean they can be ignored, however.

Over time, many of these tumors (more than half, according to some reports) invade surrounding tissues. Sometimes they begin to grow rapidly and multiply, and sometimes they do spread through the body. Here, Dr. Byron, an associate