8 Types of Dog Tumors and How to Treat Them Part 2

Histiocytoma These tumors develop through the immune system and are most prevalent in dogs three years of age or younger and in breeds including English Bulldogs, Scottish Terriers, Greyhounds, Boxers, Boston Terriers, and Chinese Shar-Peis. “These tumors are usually benign and do not spread to other parts of the body,” Swanson says. “They will typically regress on their own within two to three months, but removal may be recommended for histiocytomas that are particularly bothersome to a pet.” Histiocytomas are often referred to as “button” tumors, she adds, because they’re “frequently small (usually less than an inch), red, raised, and hairless.” They can look very similar to plasma cell tumors (or plasmacytomas), though these are more common in older dogs and generally require surgery. Hemangiosarcoma This cancer of blood vessels is most often found on the spleen, Krick says, because it has a big blood supply. “If and when it ruptures, the dog’s gums will get pale, its breathing will become labored, and it will have trouble getting up,” she says. Hemangiosarcomas can also develop on a dog’s heart and in the skin. A definitive diagnosis is made by a pathologist who examines a sample of tissue from the tumor. This often occurs after surgery to take out the spleen and resolve the internal bleeding has been performed. Chemotherapy follows surgery, Krick says, because metastasis (spread to distant sites in the body) is very common for this type of cancer. It’s most common in larger breeds like Golden Retrievers and German Shepherds. Melanoma “This is a form of cancer of the pigmented cells of the skin of dogs, and like melanoma in people, these tumors are typically black or dark brown,” Swanson says. Many skin masses are benign, but those in the mouth and at the nailbed can be very aggressive, she adds. In the case of the latter, the toe is typically swollen and may be painful. Following an x-ray, it may be determined that the affected toe must be amputated in order to fully remove the cancerous mass. The risks with this specific type of melanoma don’t end there. “It may metastasize to places such as the lymph nodes in the area and the lungs, liver, or other internal organs,” Swanson says. Once evidence of such metastasis has been identified, some combination of surgery, radiation therapy, and immunotherapy (a therapeutic vaccine for canine melanoma has been licensed by the USDA) is likely. Swanson says chemotherapy for canine melanoma is generally ineffective, as it is with human melanoma. Lymphoma Lethargy, decreased appetite, and coughing may accompany swollen lymph nodes in dogs of all breeds with this type of cancer, although some individuals initially show little in the way of symptoms other than lymph node swelling. Krick says this swelling is most noticeable under the jaw, in front of the shoulders, and behind the knees. A fine needle aspirate and/or tissue biopsy is done to reach a diagnosis. Then, a veterinary oncologist will conduct something called a staging test to determine where else in the body these cells might be, Krick says. The most common treatment is chemotherapy. Papilloma These benign tumors are warts in dogs, and Swanson says they can be uncomfortable and problematic. “When this infection develops, multiple hard, pale, cauliflower-like warts are noted typically on the lips, inside the mouth, and around the eyes,” she says. “The warts can be painful and severe infections can make chewing and swallowing difficult.” Papillomas will go away after a few weeks, sometimes months—though if they’re causing major problems for the dog in question, they can and should be removed by a veterinarian, Swanson says. These benign tumors are caused by a virus (called papillomavirus) that is transmitted by direct contact with an infected dog or contaminated objects like bedding or toys, Swanson says.