A malignant tumour arising from melanocytes (see MELANOCYTE). It may start in an existing MOLE or arise de novo. Increasing exposure to sunlight of white populations in the 20th century has resulted in an alarming increase in the incidence of this cancer. It is mainly seen in those over 40 years, especially on the legs in women and on the back in men. An enlarging pigmented macule or nodule with irregular contour, pro?le or colour distribution is always suspect.
Treatment is excision with a margin of normal tissue. The specimen must be examined histologically, and prognosis depends on the depth of invasion. Very super?cial melanomas carry an excellent outlook once removed, but deeper tumours may spread to regional lymph glands and beyond with fatal results. Public-awareness campaigns have led to the earlier presentation of melanomas in recent years, with corresponding bene?t. (See also SUNBURN.)
Any tumour of melanin-pigmented cells. Usually has highly malignant properties.
(malignant melanoma) n. a highly malignant tumour of melanin-forming cells, the *melanocytes. Such tumours usually occur in the skin (pale skin, genetic predisposition, and excessive exposure to sunlight, particularly repeated sunburn, are the most important factors); it may arise from a pre-existing mole or naevus or from apparently normal skin. It can rarely occur at other sites than the skin. Melanomas are usually dark, but may also be free of pigment (amelanotic melanomas). Spread of this cancer to other parts of the body, especially to the lymph nodes and liver, is common if the original melanoma is thick. The prognosis is inversely related to the thickness of the tumour; almost all patients with tumours less than 0.76 mm survive following surgical excision. The mainstay of treatment is surgery, but melanoma can be responsive to *immunotherapy and is currently the subject of investigational treatments using melanoma vaccines; the response rate to conventional chemotherapy is poor. Primary prevention programmes reducing episodes of sunburn are advanced in some parts of the world, such as Australia.
A raised, reddishbrown skin blemish which sometimes appears on the face or legs in early childhood (see naevus). Although they are usually harmless, an unsightly growth,or one suspected of being skin cancer, can be removed surgically.... melanoma, juvenile
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