Mast Cell Tumors – The Most Common Skin Cancer in Dogs

I had a scare with my Boston Terrier, Thumper recently. Why is that important? Because it can happen to you and your dog. Found this lump on Thumper (L) one morning. Appeared out of nowhere. Reminded me of five similar lumps that Chipper had (R) beginning at age five years. Thumper is five years old.

Chipper’s lumps were mast cell tumors, the most common form of skin cancer in dogs. They come out of nowhere, are hard to the touch, can change shape, and can be found on the paws, legs, stomach, and other parts of the body. These tumors are not “painful” so the dogs frequently will not exhibit worrisome behaviors, e.g., lethargy, not eating.

Now these tumors are not the same as histiocytomas, also known as fatty tumors, which for the most part are annoying little lumps that are usually not harmful to your dog, and while unsightly, will disappear eventually. The one below was on German Shepherd, Nabucco’s head. Long gone.

Mast cell tumors are very prevalent among certain breeds like Bostons, Boxers, Retrievers, but they can affect any dog. If you happen to see one of these on your dog, do NOT wait it out. Take your dog to the vet ASAP.

Not all mast cells are cancerous, but the majority of them are. Your vet will take aspirate the lump and then review the cells under the microscope. If the vet sees cancer cells, then a biopsy will be done and sent to an outside pathology lab. The pathologist will test and grade the tumor. Grade I is benign, but Grade II + is cancerous. The pathologist will be able to tell the vet how invasive / progressive the cancer is.

Surgery is a definite, although location of the tumor plays a large role in the success of the tumor removal and surrounding tissue. Some dogs may need radiation as a follow-up, while others won’t. In Chipper’s case, radiation was only recommended once, and I decided to forego the treatment because of Chipper’s age, 11 years, as well as his other medical issues.

As for Thumper, it was not a mast cell, but what the vet called, “infectious nodule.” He as put on clavamox, benadryl, and animax ointment. Nodule now looks like this.

And Thumper is just the same goober as he always was.