Mast Cell Tumors (MCT): Symptoms, Diagnosis, Treatment

Aimee Beck
7 min readFeb 23, 2021

What is a mast cell tumor?

Mast cell tumors (MCTs) are among the most common tumors found in dogs, and the third most common intestinal tumor found in cats. The tumor itself (aka: mastocytoma) is named after the cells that cause it. You guessed it, mast cells.

Roughly 20% of all skin tumors found in dogs are diagnosed as MCTs.

Not all mast cell tumors are malignant (cancerous). Fortunately, though, malignant MCTs are among the easiest types of cancer to treat.

Mast cell tumors most commonly appear on the skin as nodules, but can also form inside the body, affecting bone marrow, intestines, liver and spleen. They’re also commonly found on the chest, lower abdomen and on the limbs (typically the hindquarters).

Usually, mast cell tumors appear as a single growth. However, in roughly 10% of cases, MCTs have appeared in multiple locations on the body.

Large tumors, those that grow quickly, and those that manifest on the lower parts of the body, or near mucous membranes, are more likely to spread to other areas of the body.

What are mast cells?

Mast cells are a type of white blood cell. When exposed to allergens, mast cells spring into action, releasing a chemical called histamine. The release of histamine (this process is called degranulation) is what causes itching, sneezing, watery eyes, runny nose … all those things that happen during an allergic reaction.

Sometimes, when too much histamine is released into the body, it can cause anaphylaxis — a life-threatening allergic reaction.

What causes mast cell tumors?

Like most cancers, the cause of mast cell tumors is not entirely known. However, MCTs do tend to affect older dogs (over the age of 8).

While any dog is capable of developing mast cell tumors, some breeds are more susceptible, like our flat-faced friends: boxers, pugs, Boston terriers and bulldogs. Other breeds known to be affected by MCTs are Labrador retrievers, golden retrievers, Rhodesian ridgebacks and schnauzers.

Aimee Beck

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