Mast Cell Tumors in Cats

Mast cells in an animal's body go to work to repair tissues when the body has been damaged in some way. Tumors can occur in these mast cells throughout several areas of the body. These mast cell tumors, also called mastocytoma, are more common in dogs than cats. However, they are the second-most common type of tumor found in cats. Mast cell tumors can arise from the skin, spleen, lymph nodes, liver and bone marrow. In 90 percent of cases, mast cell tumors in cats are benign.

  1. Symptoms

    • Siamese cats are more likely to develop mast cell tumors than other breeds. Elderly cats are commonly victims of these tumors as well. Common symptoms of mast cell tumors in cats include rounded masses in the skin, lack of appetite, vomiting, abdominal pain and black tarry stool, which indicates bleeding in the upper intestinal tract.

    Diagnosis

    • If your veterinarian suspects your cat may be suffering from a mast cell tumor, the doctor will use several diagnostic tools. This will begin with a medical history and physical examination. There may be a needle aspiration of the skin mass or lymph nodes. The veterinarian will likely do a complete blood count and a urinalysis. She may take X-rays to examine the liver and spleen.

    Surgery

    • The doctor may use surgery as part of the diagnostic process. The tumor may be removed to determine whether it is malignant. If the tumor is benign, this may be the only treatment necessary. During surgery, the veterinarian will also remove any enlarged lymph nodes in case the tumor has spread to these areas.

      In some cases, cryosurgery--the freezing of the tumor to kill the diseased tissue--is used.

    Treatment

    • Mast cell tumors are graded on a scale of Grade I through Grade III. In many cases, the veterinarian may recommend no further treatment other than cautious surveillance for a Grade I mast cell tumor that has been removed in surgery. With a Grade III mast cell tumor, the veterinarian may refer the cat to a veterinary oncologist. Radiation or chemotherapy may then become part of your cat's treatment.

      A new treatment is a chemotherapy ointment with the name lomustine. Many cats respond well to this treatment, which is applied to the site of the tumor.

    Prognosis

    • The prognosis is good if complete surgical removal is performed on cats with Grade I mast cell tumors. More than 90 percent of these cats are disease-free after four years. For cats at the Grade II level, about 50 percent survive for four years without recurrence. In the Grade III category, prognosis is poor. With surgical removal and no use of chemotherapy or radiation, less than 10 percent of cats with this level of cancer survive for four years.