Mast Cell Tumors In Cats

Mast cells play an important role in your cat’s health. They are a type of white blood cell that performs a wide range of immune system functions, as they do in humans and other animals. Like first responders, mast cells are activated if the body is invaded by allergens, parasites and even venom from snake or insect bites. In an attempt to restore homeostasis (stable conditions within the body), mast cells release chemicals, such as histamine, which can trigger the redness, swelling, inflammation and itching that accompany allergic reactions.

Like other cells, mast cells can turn cancerous, leading to the formation of tumors. Feline mast cell tumors (MCTs) can develop on the skin, in the gastrointestinal (GI) tract or even in a cat’s spleen. This type of cancer can also metastasize to the liver or lymph nodes. At advanced stages, it can spread to the bone marrow.

Mast cell cancer in cats can be treated. The treatment course would depend on the location of the tumor(s), how far the cancer has advanced, the cat’s overall condition and other factors. Prognoses also can vary — in some cases cancer will return even if treated, but on the other hand, a cat that has a MCT removed may never get another one.

Cats that get mast cell tumors tend to be 10 or older. Some reports say they can be more common in Siamese cats, though any cat can be afflicted with this disease. It’s also worth noting that a cat with allergies may have a heightened number of mast cells, but it does not mean that cat is predisposed to developing MCTs.

Feline Mast Cell Tumor Symptoms

Tumors that form on a cat’s skin can be seen or felt. Thus, it’s a good idea to regularly examine your cat and pay attention while petting him or her to increase the chance of early detection. MCTs in a cat’s GI tract or on the spleen obviously cannot be discovered the same way. A stricken cat instead might show little desire to eat; experience vomiting, diarrhea and unexplained weight loss; and/or become lethargic. Even then, the presence of an MCT would have to be confirmed through testing, because other diseases and other types of cancer can cause the same systemics symptoms.

How Feline Mast Cell Tumors Are Diagnosed

If your cat has suspicious bumps or is displaying other symptoms discussed above, a trip to your veterinarian is in order. Standard tests when cancer is suspected include bloodwork. A complete blood count (CBC) tells us about a cat’s red blood cell level, white blood cell level and platelet count. A chemistry profile is recommended to assess organ function as well as electrolyte levels and protein levels. A urinalysis can provide information about systemic issues. For suspected internal tumors, an abdominal ultrasound likely would be recommended to provide your veterinarian with a view of the mass.

If possible, the veterinarian also typically will try to collect a sample of the tissue to send to a lab for more definitive testing. For skin tumors, a fine needle aspiration may be enough to get the sample. At times, your veterinarian may try to remove the entire mass as in a biopsy, to obtain a diagnosis this way. In the case of a GI tumor, an endoscopy might be ordered. This procedure involves using a flexible fiber-optic tube with a light and camera to reach the area of the tumor to better view it and take a sample (or biopsy). Some GI tumors, however, cannot be sampled this way. In these cases, as well as for splenic tumors, ultrasound-guided aspirates may be employed or an abdominal exploratory may ultimately be needed for biopsies. A special blood test called a buffy coat can check for circulating mast cells in the bloodstream. Your veterinarian may recommend this test to complete the work-up. Three-view chest x-rays are recommended to assess the cat’s lungs and heart. The full battery of these tests can also help determine whether the cancer is metastatic (meaning it has spread) and to rule out other types of cancer, such as lymphoma, adenocarcinoma, or sarcomas.

Treatment Options and Prognosis

The recommended course of treatment for mast cell tumors in cats largely depends on their location and the amount of disease. Veterinarians have a wide range of options to consider in their mission to achieve the best outcome.

Cat getting a checkup

Skin Tumors

  • Surgery is often the treatment of choice, especially when a cat only has a solitary tumor or a couple of tumors. Sometimes when a bump is removed the cat will never develop another one.
  • When mast cell tumors in cats appear in clusters or a cat has masses or nodules in multiple places, surgery may not be viable. In these instances, chemotherapy with a medical oncologist is indicated. There are intravenous (IV) and oral forms. The majority of cats handle chemotherapy quite well, with only a small possibility of vomiting, diarrhea or loss of appetite as side effects. They generally do not lose fur, either, though some might lose whiskers.
  • A steroid called prednisone also can help if a cat has numerous nodules. Prednisone can kill some mast cells, thus shrinking tumors or slowing them down to help the cat’s condition for a few months.

Splenic Tumors

  • The spleen is an organ that filters blood, among many other functions, but it is not essential for life as an adult. Thus, if your cat develops a splenic tumor, surgical removal is the preferred treatment option. Removal typically will greatly help your cat’s quality of life. Surgery can be followed up with chemotherapy to slow recurrence. As mentioned earlier, cats tend to handle chemo well. This protocol may require regular vet visits, perhaps monthly or more frequently. If the cancer has metastasized, removal of the spleen often still helps a cat feel better even if it doesn’t stop the cancer’s progression.
  • An alternative is prescribing prednisone, which will help kill some mast cells and shrink or slow down tumor growth. This regimen could help a cat’s prognosis and quality of life for a few months.

GI Tract Tumors

  • The removal of MCTs in the GI tract is recommended if possible, but this kind of cancer tends to return even with removal. Thus, chemotherapy also might be recommended. A veterinary oncologist might suggest oral chemo or an injectable form. The cat’s prognosis depends on how aggressive the cancer is; treatment could help for anywhere from a few months to a year and a half.
  • For quality of life, an antacid such as Pepcid can help, because mast cells can cause the stomach to secrete too much acid.
  • If MCTs in the GI tract are left untreated, symptoms will persist. Eventually, the cat parents will have to make a quality-of-life decision about whether to euthanize their pet.

PetCure Oncology and Treatment of MCTs

PetCure Oncology’s mission is to provide pets with the best treatment options available for any type of cancer, including mast cell tumors in cats. If your cat requires the services of our veterinary oncology specialists, you can expect the utmost compassion and will learn firsthand why our motto is “We understand. We commit. We will help.” To learn more about our treatment options and how deeply we care, find a location near you and contact us today.

The contents of this article were provided in part by Dr. Renee Alsarraf, DVM, DACVIM (Oncology), a board-certified veterinary medical oncologist and member of PetCure Radiation Oncology Specialists (PROS).

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