Melanocytic Tumors of the Skin and Digits (Melanoma)
What are melanocytic tumors of the skin and digits (toes)?
Melanocytes are cells in the skin or gums that produce pigment or melanin. A melanocytic tumor of the skin or toes is a tumor that arises from melanin-producing cells in these locations. These tumors are also known as melanomas. They can be benign or malignant. Benign tumors can invade the local area around the tumor. Malignant melanoma can spread (metastasize) to bone, lymph nodes, lungs, and abdominal organs. Melanocytic tumors of the skin and digits are fairly common in dogs. Scottish terriers, Boston terriers, Airedale terriers, cocker spaniels, boxers, English springer spaniels, Irish setters, Irish terriers, chow chows, Chihuahuas, and Doberman pinschers are the more commonly affected breeds. The tumors may be more common in male dogs than in female dogs. Melanocytic tumors of the skin and digits are also seen in cats, though without any breed predilections.
What causes melanocytic tumors of the skin and digits?
The cause is unknown.
What are the signs of melanocytic tumors of the skin and digits?
A melanocytic tumor of the skin is a solitary mass that can occur anywhere on the skin, but is more common on the face, trunk, feet, and scrotum in dogs, and the head and ears (pinnae) in cats. Masses vary in color and appearance. In general, benign melanoma is slow growing, brown to black, and varies from small flat spots to firm, small, dome-shaped nodules. Usually, malignant melanoma is rapidly growing. Malignant melanoma may not be pigmented or may be dark brown, gray, or black. Both benign and malignant melanoma may be ulcerated. Melanoma involving the toes in dogs and eyelids in cats tend to be malignant. If a toe is affected, the animal may be lame. The lymph nodes around the mass may be enlarged. In advanced disease, the animal may have difficulty breathing because of spread (metastasis) of the cancer into the lungs.
How are melanocytic tumors of the skin and digits diagnosed?
It is often difficult to distinguish benign tumors from malignant tumors. Melanocytic tumors of the skin and digits are diagnosed by microscopic examination of a sample of the tumor. Special stains (dyes used to color cells and tissue for better visualization under the microscope) are used to help differentiate melanoma from other tumors. Radiographs (X-rays) of the chest may be done to evaluate spread of the cancer into the lungs. Radiographs also may be done of the tumor area to determine if underlying bone is involved, especially in animals with melanoma of a toe.
How are melanocytic tumors of the skin and digits treated?
Early surgical removal is vitally important because malignant melanoma may spread early in the disease and is a life-threatening condition. The tumor and a wide margin around the tumor are removed. If the toe is involved, it is amputated. Drug therapy (chemotherapy) is recommended if the tumor cannot be removed completely. Chemotherapeutic drugs have potential serious side effects.
What is the prognosis (outcome) for pets with melanocytic tumors of the skin and digits (toes)?
The prognosis for animals with melanocytic tumors of the skin and digits varies based on characteristics of the tumor. Dogs with benign melanomas have lived over 2 years. Dogs with malignant melanoma generally live less than 2 years; those with tumors of the digits have a poorer prognosis. Cats may live less than 6 months.
The information on this page was obtained from the site www.vetmedcenter.com