Treating Pets’ Cancerous Lumps and Bumps

By Dr. Laura Hady

Last month, I discussed diagnosing lumps and bumps on our beloved pets. Today is a follow-up to that, providing information about how the more common cancerous ones can be treated in our middle-aged to older pets.

In dogs, mast cell tumors are the most common, while squamous cell carcinomas top the list in cats. Cancer therapy is constantly evolving due to biotechnical and pharmaceutical advances in the veterinary world. Since the diagnosis of tumors and treatment can be overwhelming, I have some tips that may help you digest all the information that you will receive, or you can read more on

  • Mast cell tumors are often called the “great pretenders” because they can look like so many other benign masses and cysts. If you note that a small bump on your pet’s skin has doubled in size or has become ulcerated, let your family veterinarian know as soon as possible. Mast cell tumors can release a life-threatening amount of histamine into your pet’s body, which can cause bruising of the skin, a life-threatening decrease in blood pressure (hypotension), and heart abnormalities. A first-line treatment consisting of steroids and antihistamines may be prescribed to shrink the tumor and help lessen the effects of a histamine release. Mast cell tumors can spread (metastasize) to the lymph nodes, spleen, and liver. Surgical removal is often the treatment of choice, with the removal of an extra 3 centimeters of tissue around the mass recommended to make sure that the tumor does not regrow in that location. Your family veterinarian may be able to use an injection to kill off the tumor if it is lower grade and found on the limbs. A referral to a veterinary oncologist for follow-up care is also a viable option depending on the location and stage of the mast cell tumor.
  • Squamous cell carcinomas are often ulcerated and found on sparsely haired areas of the skin. They tend to be more prevalent in white cats and can be found near the eyes, ear tips, and in the mouth. The key to fighting this type of tumor is catching it early and treating it aggressively. The first step will be to see if this tumor has spread to other parts of the body, such as the local lymph nodes and lungs. Blood work should help your veterinary staff decide if your pet is a good candidate for surgical removal of the mass. Other treatments include freezing the tumor, light therapy, radiation therapy, and chemotherapy.
  • Soft tissue sarcomas are a group of about four different tumors found under the skin in connective tissues that support the body, like ligaments, tendons, and the covering of muscles called fascia. The masses are often firm, tend to invade the local tissues, and cause pain. Soft tissue sarcomas can spread to other parts of the body if they are staged as high-grade tumors based upon microscopic appearance and location. Surgery is the best treatment option, but please know that these tumors can recur. If the mass is on a part of the leg that does not have a lot of skin, removal and skin grafts, or amputation of the limb may be recommended. If additional surgery is not an option, chemotherapy or radiation therapy will be options to make your pet more comfortable and slow the spread of the tumor. My recommendation is to remove these tumors when they are first noticed because of the potential for local invasion into the surrounding tissues.
  • Melanomas are tumors arising from pigment cells in the body. They are typically dark or flesh colored. Melanomas most commonly occur on the skin, inside the mouth, near the toes, and on the anus. Dogs tend to have the more malignant forms of melanomas, which can quickly spread to other tissues and organs. Cats can get melanomas in their eyes, especially in the iris. When melanomas are in the mouth, they tend to cause drooling, bad breath, and oral pain. Your family veterinarian may recommend chest radiographs before removal of the tumor to make sure the melanoma has not spread to the lungs. There is a vaccine called Oncept that stimulates your dog’s immune system to attack any additional tumor cells after the bulk of the tumor has been removed.

Hearing the word “cancer” is scary for all of us, especially when our pets can’t always tell us that they have something that feels funny underneath their skin. Please consult your family veterinarian about the side effects of therapy, chances for recurrence, and what to expect of the quality of life for your pet. Rainbow Bridge’s Pets with Cancer Chat Room ( and FETCH a Cure Pet Cancer Support Group ( are just two of many groups that provide education, funding, and emotional support to help you navigate the maze of decisions you may face.

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