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melanomaA tumour that comprises 1–3% of all new cancers (18,000/year) and causes 6500 deaths/year (US), most age 30–50; melanoma is increasing at ± 7%/year, and now affects 9/105 (primarily the head and neck) in men and 12/105 (primarily legs) in women; it is rare but more aggressive in children.
Giant congential melanocytic nevus, dysplastic nevus, xeroderma pigmentosum, immunodeficiency, moles with persistent pigment changes (especially > age 15), large or irregularly pigmented lesions, familial moles, congenital moles, Caucasian (12-fold greater risk than Black), previous melanoma, melanoma in 1st-degree relative, immunosuppression, photosensitivity, increased sun exposure.
Site of metastasis
Liver, lung, intestine, pancreas, adrenal, heart, kidney, brain, spleen, thyroid.
Wide excision; chemo- and radiation are essentially useless.
Local recurrence common; many metastasise; 5-year survival reflects stage when diagnosed.
Poor prognostic factors
Large size, paranasal/nasopharyngeal location, vascular invasion, high mitotic activity, marked cellular pleomorphism, distant metastases.
Stages of melanoma
▪ Stage I—Confined to epidermis and/or upper dermis, and measures ≤ 1.5-mm thick.
▪ Stage II—1.5-mm to 4-mm thick; spread to lower dermis but not beyond or to adjacent lymph nodes.
▪ Stage III—Any of the following:
– > 4-mm thick;
– Spread beyond the skin;
– Satellite lesions within 2 cms of the original tumour; or
– Spread to nearby lymph nodes or satellite lesions between original and regional lymph nodes.
▪ Stage IV—Metastases to other organs or to lymph nodes far from the original lesion.
Types of melanoma
Acral lentiginous melanoma
A rare, flat, palmoplantar or subungual lesion more common in non-whites; average 5-year survival < 50%; unrelated to actinic exposure, but possibly related to ectopic pigmentation.
Rare, poorly differentiated, and occurs in those with a previous pigmented melanoma; since the Fontana-Masson stain is rarely positive in amelanotic melanoma, special studies are necessary, including immunoperoxidase staining with antibodies to the S-100 antigen and ultrastructural examination for presence of premelanosomes.
Comprises 10% of melanomas; affects those > age 60; appears as flat, indolent lesions on face, arising from a premalignant freckle with greater than 90% 5-year survival; aetiologically linked to prolonged actinic exposure.
15% of cases; similar clinically to superficial spreading melanoma; 50% average 5-year survival.
1/3 of lentigo maligna (Hutchinson’s freckle) progress to malignant melanoma after 10–15 years.
Superficial spreading melanoma
70% of cases; affects ages 30 to 60, especially female in lower legs or trunk, as a flat lesion (radial growth phase) that may be present for months to years; average 5-year survival 75%; aetiologically linked to recreational actinic exposure.
Thin melanoma (Stage-I cutaneous melanoma)
A lesion measuring < 1 cm in diameter; virtually 100% survival.
melanosarcoma(mĕl″ă-nō-săr-kō′mă) [″ + sarx, flesh, + oma, tumor]
Sarcoma containing melanin.