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Mast Cell Tumors in Dogs

Mast Cell Tumors in Dogs

Mast cell tumors in dogs, also known as Mastocytoma, are very painful and dangerous. Let us see what this condition entails and how to treat it.
Rujuta Borkar
Mast cell tumors in dogs (mastocytoma) is one of the most common form of tumors that a dog can be afflicted with. These tumors grow out of the mast cells which are present in the tissues of the body. Mast cell tumors also affect a lot of other animals, but they are mostly benign. However, when these tumors affect dogs they lead to the growth of cancerous cells which could eventually lead to cancer. Mast cells are connected to the immune system as they have within themselves histamine, heparin and protein-breaking enzymes―these are responsible for fighting parasites and foreign invaders. However, when the tumors develop in dogs, these very enzymes can lead to a lot of damage. The tumors can affect dogs of all ages, but they are a common occurrence in older dogs. Golden Retrievers, Boxers, English Bulldogs, and Cocker Spaniels are some of the breeds that are most commonly affected by this illness.


A mast cell tumor can develop anywhere on the dog's body and is usually found in the superficial layers of the skin. Here are some symptoms of the same.
  • The most common sign to look out for in this form of tumor is a lump/hump in/on the skin.
  • It is a raised mass and is usually pink or red in color.
  • Although it can develop all over the body, it is most commonly found in the genital areas, trunk, or the limbs.
  • Usually, there is more than one tumor.
  • These lumps can be benign, smooth and bumpy, or ulcerated.
  • It is for this reason that the tumors are termed as the great pretenders.
  • There may be visible thickening of the skin.
  • The dog will constantly try to scratch the area or rub against it because it is a very painful disease.
  • The tumor may cause black stools and bleeding in dogs.
  • There will be a loss of appetite.
  • There will also be vomiting and abdominal pain.

There are mainly three methods that are adopted for the use of treatment. These include:
  • Radiation Therapy
  • Chemotherapy
  • Surgery
Radiation Therapy
Radiation therapy is used in conditions when the tumors are localized and few. This therapy cannot be used on dogs that have been inflicted with the disease throughout the body or those who have developed multiple tumors, because this involves using a radiation beam that has a single focus on the disease. Dogs take well to this therapy and the chances of the tumors returning are lessened considerably. Although it is a little expensive, this therapy has proved to be the most effective as far as localized tumors are concerned.

Chemotherapy is used most effectively in conditions when multiple mast cell tumors develop. This form of therapy uses anti-cancer drugs for delaying the growth and spread of the cancerous tumors. Chemotherapy involves using drugs like lomustine, vinblastine, and prednisolone which is a cortisone. These drugs might be administered before, during, or after a surgery, or might be individually administered. The duration of the drugs administered will depend on the stage of the tumor. The doctor will discontinue the medication if there are no more tumors formed. There are certain side effects that are seen as well.

When there are single mast cell tumors involved, performing a surgical procedure is considered the best option. This procedure is called 'Wide Resection'. This involves removing the damaged tissue and at least 3 cms of surrounding normal tissue, so that the malignant tissue does not spread to the other parts of the body. Many times, however, the mast cells are very invasive and therefore removing them entirely is impossible. Surgeries have often been successful for stage II tumors as well. A surgery is usually used as the first option because this will determine what other forms of therapy need to be used.


The prognosis is mainly based on the grade and stage of the tumor. The further advanced the tumor, the prognosis will be grim. However, a timely detection of the tumor will ensure that there is success in the treatment procedure. Usually, stage I and stage II tumors that have been successfully removed through surgery or a combination of surgery and other therapies have a lesser chance of recurring. The prognosis is different for different dogs.

When the mast cell tumors are detected at an early stage and dealt in the best possible manner, there are chances that they will not reappear again. So keep a look out and if you find a lump on the dog or notice any of the other physical or physiological signs, then make sure that you consult your doctor immediately.

Disclaimer - This DogAppy article is for informative purposes only, and should not be used as a replacement for expert medical advice.