Mast cell tumors most often appear on the skin. There is a lot of variation in their appearance, but they’re most commonly hairless, ulcerated and pink or red in color.
In addition, the tumor may swell or develop hives in response to rubbing. Occasionally, a mast cell tumor will be completely under the skin and feel like a lump. And sometimes, a dog will have more than one.
Even if you believe you’ve correctly identified a growth or lump on your dog, it’s impossible to determine what it is, and whether it’s benign or malignant, with just a visual inspection. A mast cell tumor must be examined and removed by a veterinarian to determine whether it indicates a threat to your dog’s health.