Vet Examining Dog
If you happen to find a lump on your pet, it can be a panic-provoking moment. But even if the bump that you thought was a simple pimple turns out to be a malignancy, chances are that it can be effectively treated.

Successful treatment of skin cancer in pets involves a biopsy to determine the exact type of tumor and, in most cases, surgery to remove the tumor, as well as possible follow-up chemotherapy or radiation therapy. For tumors that are difficult to manage, your veterinarian may refer you to a specialist trained in veterinary oncology, radiation or surgery.

Here's a look at some common cancers found in dogs and cats, and the expected courses of treatment — plus what you can do to be a proactive pet parent.

Mom Was Right: Grades Do Matter

All malignancies are not the same — even if they have the same name.

Take, for example, the most common malignant skin tumor found in dogs: the mast cell tumor. These tumors can range from relatively benign to white-hot malignant. When pathologists examine the biopsy sample under a microscope, they can predict the behavior of such tumors.

In nearly all dogs with a grade I mast cell tumor, surgical removal cures the dog. Dogs unlucky enough to have a grade III mast cell tumor usually need chemotherapy follow-up because they have a form of the disease that will most likely spread throughout the body. The treatment protocol for dogs diagnosed with a grade II mast cell tumor falls somewhere between grades I and III.

Soft Tissue Sarcomas Attack With Tentacles

Surgical excision is especially important for treating a group of skin tumors known as soft tissue sarcomas. These tumors arise from the cells of soft tissue structures, such as blood vessels, nerves, muscle, connective tissue and cartilage. The nature of soft tissue sarcomas is to send tentacles of malignant cells out into surrounding tissues.

If your pet undergoes surgery for the removal of a soft tissue sarcoma, the incision will be much larger than you likely expected, since a wide margin of normal-appearing tissue must be removed to excise every last tumor cell. If the biopsy indicates tumor cells were not completely removed, your veterinarian will likely recommend more surgery or radiation therapy.

A Cancer Imposter in Cats

Occasionally, what a pet owner thinks is cancer actually turns out to be something completely benign, such as lentigo simplex in orange cats.

As your orange tabby cat ages, he may start to get little, dark spots on his lips and gums. These spots typically increase in number and size as your cat gets older. The flat, dark spots are accumulations of pigment in the skin, but this pigment is normal, unlike an accumulation of malignant pigment cells known as melanoma.

Lentigo simplex is much more common in cats than melanoma, but if you find dark spots of any kind on your cat, be sure to bring it to the attention of your veterinarian.

Proactive Cancer Prevention

When it comes to catching cancer early, one of the most important things that you can do is one of the simplest: Look at your pet — not just with adoring eyes, but with a critical mind. Ask yourself if you see anything different from the last time you gave him a once-over.

You should also pet your dog or cat — all over. Pay attention to what you're feeling as you stroke the coat, making sure to notice any lumps or bumps. Brushing or combing your pet daily is another way to become familiar with his anatomy and unwanted growths.

If you find a lump on your pet, make an appointment to see your veterinarian. If you have a light-coated pet, mark the fur near the mass with a permanent marker to help locate it once you get to the vet. Dark-coated pets are a challenge, but a well-placed swipe of Wite-Out® works well — or snap a photo with your smartphone.

Dr. Ann Hohenhaus, a practicing veterinarian for 25 years, is board-certified in both oncology and internal medicine. She maintains her clinical practice at The Animal Medical Center in New York City, providing primary care to her long-term patients and specialty care to pets with cancer and blood disorders.