Canine Health Menu

Melanoma

Issue Description
Melanoma is a type of cancer that occurs commonly in dogs with pigmented (dark) skin. Melanomas can occur in areas of haired skin, where they usually form small, dark (brown to black) lumps, but can also appear as large, flat, wrinkled masses. Melanomas also can occur in the mouth, toes, or behind the eye. In general, skin melanomas tend to be benign, and those in the mouth, toes, or eyes tend to be malignant.
Other Names
Canine Melanoma


Causes
Melanoma arises from melanocytes, cells that impart pigment or coloration to the skin. In humans, melanoma arises due to mutations induced by repeated, intense exposure to ultraviolet light (for example, frequent tanning or working outdoors). This does not seem to be a major factor in dogs, as in most breeds the hair coat affords them protection from sunlight. However, pigment cells divide every time there is injury to the skin, or if there is constant trauma (for example, areas where dogs constantly scratch or lick). Nevertheless, risk factors for Melanoma are not well established.

Mutations that contribute to cancer can also be inherited. An inherited mutation in a single gene that is important in cell growth control will increase the risk of that individual to develop cancer. This can be due to reducing the overall number of acquired mutations that must accumulate before a cell becomes cancerous, or it can be due to disabling a critical safeguard gene that normally prevents cells from becoming tumors. Specific genes that are responsible for familial melanoma have been identified in humans and in mice. In dogs, there appears to be a predisposition among certain breeds or families to develop specific types of cancer, suggesting that a hereditary component may be important in the development or progression of the disease.


Common Symptoms Of Cancer
  • Hesitation to exercise or loss of energy.
  • Loss of appetite, weight loss.
  • Persistent lameness or stiffness of movement.
  • Lumps in the breast area.
  • Abnormality or difference in size of testicles.
  • Abnormal swellings that continue to grow, especially in the nymph nodes.
  • Sores do not heal.
  • Bleeding or discharge from the mouth, nose, urinary tract, rectum, or vagina.
  • Offensive odor.
  • Difficulty eating or swallowing.
  • Difficulty breathing.
  • Difficulty in urinating or defecating.


  • Diagnosis
    A physical exam, blood tests, a chest x-ray and a biopsy when the veterinarian believes it is necessary.

    Treatment
    Treatment of melanoma includes surgery, chemotherapy and radiation. Surgery will be performed to remove as much of the tumor as possible. Chemotherapy is used including Dacarbazine. Radiation is used as a treatment because it aides in the shrinking of the tumor.

    Prognosis
    The prognosis for Melanoma is poor at best when found in the dog's skin. The prognosis for Melanoma is even poorer when it is located in the mouth, toes or behind the eyes. Tumors spread quickly when they are not treated and they may spread even if treatment is tried. Melanoma may even reoccur after treatment.

    Dogs
    Horse Herd