Mast Cell Tumours


Mast cells are cells that reside in the connective tissues, especially those vessels and nerves that are closest to the external surfaces (e.g.lungs, nose, mouth, skin). Mast cells contain histamine and heparin. They play a role in allergic responses, non-allergic skin disease, and wound healing.

When mast cells replicate in high numbers in an abnormal manner, a mast cell tumour can form. Pets with mast cell tumours can develop complications like excessive bleeding from the release of heparin and stomach problems from the overproduction of histamine.

Mast cell tumours can develop in both cats and dogs. While some are benign, most of these tumours are malignant. Cats tend to develop multiple tumours, while dogs tend to have single tumours.

The cause of mast cell tumours is unknown. As with other tumours, mast cell tumours begin with raised bumps or growths with an escalation of symptoms depending on the severity of the condition and whether the tumour is cancerous. The symptoms include:

  • Redness or irritation of bump
  • Raised growth or bump
  • Loss of hair in area of bump
  • Ulceration – if your pet irritates the mass or in severe cases of cancerous tumour

In cats, mast cell tumours are most often seen in the skin of the head or neck. Siamese cats are at higher risk than other breeds. In dogs, mast cell tumours are most often found on the limbs, trunk, and in between the toes. Boxers, English bulldogs, bull terriers, fox terriers, and Labradors, have a higher tendency to develop mast cell tumours.

Diagnosis of mast cell tumour in your pet begins with a physical exam. Your vet will examine the suspected tumour and will search your pet for any other possible tumours located in other parts of the body. Your vet will subsequently conduct a biopsy of the tumour.

If your vet determines the tumour is malignant, he or she may order additional tests to determine whether cancer has spread to any other organs.

In cases where cancer has spread, chemotherapy may be recommended. During chemotherapy, special drugs attack the cancer cells, causing them to shrink or disappear. Chemotherapy is usually administered in several treatments over a prolonged period.

The preferred treatment for mast cell tumours in cats is surgical removal of the tumour. Your vet may order a full blood panel to ensure there are no additional conditions that would make surgery risky for your pet. Your vet will attempt to remove as much of the tumour as possible. This means they may have to remove extra tissue around the edges of the tumour to ensure that all the cancerous cells have been removed.

After surgery, your pet will need routine follow-up appointments with your vet and will require careful monitoring on the owner’s part to ensure that tumours do not return.