A “tumor” is simply a swelling. There are many different causes of swellings. Abscesses, insect bites, allergic reactions, and cancer are just some of the causes. Your pet’s veterinarian can distinguish between these causes by a physical exam, history and sometimes other diagnostic tests. Each cause has its own individual treatment.

Tumors caused by cancer can be benign or malignant. Benign tumors do not spread to other parts of the body. Malignant tumors usually carry a worse prognosis and have the potential to spread to other parts of the body. Tumors can arise from any type of tissue including bone, skin, internal organs, and even nerve sheaths. Clinical signs of tumors include a swelling. You may feel a swelling under your pet’s skin, or see one in their mouth or ear. The only way to diagnose whether the tumor is benign or malignant, and what type of cell it came from (which dictates prognosis and treatment options), is to obtain cells from the tumor and look at them under a microscope. Your veterinarian might obtain cells by inserting a needle into the tumor (called a “fine needle aspirate”) or by obtaining a chunk of cells, or a biopsy. Fine needle aspirates provide a diagnosis about 70% of the time. Biopsies provide diagnosis almost 100% of the time, but are more invasive, usually more expensive, and may require sedation or general anesthesia to obtain. Treatment and prognosis depend on what the cells or tissue look like under the microscope and what tissue they arose from. Sometimes surgery can be curative, however some tumors require additional surgery, radiation therapy, or chemotherapy.