(1997; 132 pages) [French] [Spanish]
Malignant melanoma resulting from malignant changes in cutaneous melanocytes is the most fatal form of skin cancer. None the less, with proper early diagnosis and adequate excision of the lesions, most melanomas can be treated without long-term consequences. Most melanomas develop from the normal melanocyte population of the skin, but 30-40% may arise from pre-existing moles. Signs that malignant changes may be occurring (although not predictive in themselves) include a rapid change in size, a change in colour (with or without spread of pigment to the adjacent skin), inflammation of the surrounding skin, and bleeding or ulceration of a pigmented lesion. Early lesions may be flat and look like an unusual freckle. The colour is not uniform with areas of dark coloration contrasting with light areas. This variation in colour is a particularly important sign.
Suspicious lesions that are small in size (e.g. diameter ≤ 6 mm) should be excised with a border of 3-4 mm initially. If the lesions are too large to excise, biopsies should be taken for histological examination. The depth of the lesion should be determined, if possible, as this is important in deciding whether additional surgery is required and is also essential for prognosis. Re-excision of margins of normal skin between 1 and 2 cm in width around the original tumour may be done, depending on the depth of invasion found on histological examination. The depth of invasion in the skin is also an important factor in determining the potential for the lesion to metastasize to distant sites.