Mastocytoma is a solid tumor consisting of a dense infiltration of mast cells. Mast cells are involved in allergic reaction. They release histamine, which causes irritation and itching, and other chemicals that may cause shock. Mast cell tumors may be seen in dogs of all ages but occur most commonly in dogs 8 to 10 years old. They may develop anywhere on the body surface as well as in internal organs, but the limbs, especially the back of the upper thigh, lower abdomen and chest are the most common areas. Many breeds are affected by this condition, especially the Boxer, Pug, and Boston Terrier. Boxers often have mast cell growths on their ears.
The mastocytoma is sometimes called as "the great deceiver" as it can show up with a wide range of appearances and clinical signs. The skin growths of mast cell tumors can be single or multiple, small and pale, or large, red and inflamed. They can be superficial or deeper in the dermis. The size of the growth may change. Those changes are the result of histamine release by the cancer. Touching or rubbing the growth may cause it to grow and become red and inflamed. Rarely, dogs will show signs of stomach upset and gastric ulcers (such as vomiting and black stool); interference with blood clotting and kidney inflammation.
Treatment of mast cell tumors employs a wide variety of techniques because of the stubborn nature of this type of tumors. Surgical removal of the effected and surrounding areas of the skin is usually the first step taken. Following surgical recovery, extensive radiation therapy and chemotherapy may be employed to help reduce the chances of recurrence and metastatic growth. Cryotherapy is also used in those instances in which surgical removal of the tumor is incomplete or impossible.