Mast cells are one of the white blood cells involved in the body’s immune system, especially the allergic reaction response. When certain materials (such as the proteins associated with insect bites and stings) enter the body, Mast cells are activated and release a number of chemicals (especially histamine) which bring about local swelling, redness and inflammation. These chemicals cause blood vessels to dilate and become more permeable so that other inflammatory cells can enter the area of inflammation.

Mast cells are found throughout the body. They are more concentrated in the skin, spleen and lymphnodes in general.

Like any other cell in the body, Mast cells can become cancerous. When this occurs, they can create localized solid tumors, and/or can develop into circulating tumor cells. Cancerous mast cells have a tendency to release their chemicals randomly which can lead to problems throughout the body. In particular, when mast cells release histamine, it can cause destruction of the protective mucus layer in the stomach which can then lead to bleeding ulcers. When solid mast cell tumors are traumatized (by bumping or manipulation) they may release their chemicals which can lead to abrupt swelling in the area. Sometimes, so many blood vessel dilating chemicals are released that the blood pressure can collapse suddenly and the pet may collapse.

How do our veterinarians diagnose Mast Cell Tumors?

Mast cells are known as the great masqueraders of cancer cells. Any lump can potentially be a mast cell tumor. The only way to diagnose the tumor is by observing the abnormal mast cells in the tumor. This can be done by aspirating a small amount of material from the lump and observing it under a microscope. Alternately, when our veterinarians remove tumors we typically send them to the lab for analysis and the pathologists will make the diagnosis.

What is the prognosis if my pet has mast cell tumor?

Mast cell tumors are found in 3 levels of severity. Grade one mast cell tumors look very much like normal mast cells and when they are surgically excised, the disease is often times cured. Whenever our veterinary team excise a mast cell, we need to have the pathologists check the margins of the tumor to make certain that we got all the cells out. If the margins of the excised tissue contain mast cells, then a second more radical surgery is indicated.

Grade II mast cells are more aggressive than grade I tumors. They have a greater tendency to spread to the local lymph nodes and into the body into the spleen, liver or lungs. Therefore, when we receive a diagnosis of grade II or III disease, then we need to do a series of tests to see if the tumor has spread internally. This is accomplished by means of xrays of the chest and belly, ultrasound guided aspiration of the spleen and a blood test to check for circulating mast cells (buffy coat examination). If our veterinary team get clean margins on the pathology report and no evidence of internal tumors from out testing, then the prognosis is not bad. The median survival time for these patients is approximately 2-3 years. However, recurrence of the tumors is not uncommon.

Grade III tumors are very aggressive and tend to spread all over the body. They can be very difficult to remove surgically.

Can Mast Cell tumors be treated with medicine?

There are a number of different chemotherapy protocols that can be used to help reduce recurrence of mast cell tumors and to lessen the side effects related to the histamine release from the tumors. Chemotherapy is considered in the face of Grade II or III disease. All pets with mast cell disease are usually placed on histamine blockers to help protect the stomach from ulceration. Chemotherapy response rates vary with the severity of the initial disease. Our veterinarians can discuss the statistics with you if the need arises.

All pets of Alta Loma, Rancho Cucamonga, Upland, Ontario, Claremont, Fontana and the Inland Empire with mast cell disease should have comprehensive physical examinations 2-3 times per year. Radiographs should be repeated at 4-6 month intervals to check for internal disease.