Cancer is actually an uncontrolled growth of cells resulting from an accumulation of changes in the structure of the genes that control cell division and multiplication. Melanoma is one of the several malignant neoplasms, usually of the skin. The affected cell is mostly melanocytes, a cell in the basal layer of the epidermis that produces melanin under the control of the melanocyte-stimulating hormone. Benign and malignant skin tumors are a common form of canine and feline cancer.
Melanoma cancer in dogs occurs commonly in dark skinned animals, usually in areas under haired skin, as small, dark brown to black lumps. In certain cases they may appear as large flat wrinkled masses. Other areas where melanomas can also appear include mouth, digits and behind the eye. A swelling or increase in size of lymph nodes is the first clinical sign of a malignant melanoma. Although the pigment called melanin is the distinctive characteristic of such tumors, some melanomas may not display a darkly colored pigment.
Malignancy is established with the aid of a microscopic examination. For this purpose a small piece of the tumor is cut off and evaluated. The pathologist then grades the melanoma according to how rapidly the cells are proliferating. This gives an estimate of the likelihood of metastasis.
The best treatment of melanoma is a total excision through surgery. To be on the safer side, the surgeon may remove some of the neighboring tissue as well. If the tumor is confined to a particular area this amounts to a full cure. The excised sample is again sent for histological examination to ascertain whether the entire tumor has been removed or not.
Melanomas can also spread to distant organs in the body. Complete remission in such cases is rare and it affects the long term survival of the dog to a great extent. Once the tumor has metastasized, cancer can start presenting itself as varied symptoms like the symptoms of liver cancer in dogs.
To the relief of dog owners, all moles in the skin are not malignant. It is normal for a dog or a cat to have dark pigmented areas of skin, particularly in the tongue, gum and eyelid tissue. As a general rule small skin tumors tend to be benign and the ones in the mouth toes, fingers or eyes are mostly malignant. Benign melanomas are seen as dark masses up to two inches in diameter. Unless the mole or a lump starts increasing in size, or elevates above the surface of the skin or bleeds, there is no need to worry. Such a condition necessitates an examination of the lump that you may see on the surface of your dog’s skin.