Canine melanoma, one of the five most frequently diagnosed cancers, can develop in many places on a dog’s body. The way the tumor behaves varies with its location.
What is it? A canine melanoma arises in pigment cells on the skin (where, unlike human melanomas, it’s usually benign), in the mouth, in the nailbed (toenail) or footpads, or in the eye. While human melanomas are generally the result of too much sun, that doesn’t seem to be the case for dogs. Light-colored dogs are rarely affected by a melanoma; it’s more commonly found in dogs with dark coats and darkly pigmented skin. Oral melanoma (OMM) is the most common form and is often discovered during a routine examination or by the owner. It may appear on a dog’s gums, lips, tongue or hard palate.
via Whisker Therapy