Mast Cell Tumor in Siamese Breed Cats

Cutaneous mast cell tumors occur widely in cats, especially the Siamese breed. The histiocytic (derived from bone marrow) mast cell variant occurs predominantly in Siamese. The breed appears to be genetically predisposed to mast cell tumors, according to Robinson Veterinary Services. The majority of mast cell tumors are malignant and require prompt treatment to extend the cat's life.

  1. Occurrence

    • Most mast cell tumors occur on the skin but they can also be found on internal organs such as the spleen. Advanced cutaneous malignant mast cell tumors easily spread to the internal organs. The malignancy commonly occurs in older dogs and cats, except the Siamese. The average age of mast cell tumor onset in the Siamese is 4 years.

    Histamine

    • Mast cell tumors of the skin contain histamines, which cause the tumor to react with an inflammatory reaction when the tumor is touched, turning red and warm to the touch. With widespread mast tumors the histamines are released throughout the body which renders the cat's blood pressure extremely low. The cat can even slip into shock as a result of handling or touching its skin tumor too much.

    Appearance

    • The Siamese cat can exhibit tumors on the skin that appear as small, red lumps if suffering from mast cell carcinoma. If the tumor has spread to the internal organs the cat will often begin to vomit, suffer lethargy and weight loss.

    Diagnosis

    • Once a mast cell tumor is suspected, the veterinarian will take a needle biopsy. He will insert a needle into the location to collect cells. Often a mast cell tumor will continue to bleed for up to an hour after the biopsy. The veterinarian may perform X-rays and an ultrasound on the cat to see if the tumor has spread to other organs of the body.

    Treatment

    • Benign mast cell tumors are easily removed surgically. Malignant mast cell tumors can also benefit from surgical removal. If the mast cell tumor has spread to the cat's spleen the veterinarian will normally remove the skin mast cell tumor and the spleen of the infected cat. Siamese cats who have had their spleen removed and their cancerous skin tumors surgically excised often survive about a year. Cats with cancer spread to other areas of the body normally only live a few months. Prednisone and chemotherapy drugs are often prescribed for treatment but the prognosis is usually poor. Histamine blocking drugs also help reduce the risk of low blood pressure and shock occurring during the cat's remaining time.