Most common variety of malignant melanoma:

Ref: Rook's Textbook of DermatologyExplanation:Superficial spreading melanoma is by far the most frequent type of melanoma.The most common sites: In female - leg and the In males - back.If the melanoma is developing in a pre-existing naevus, which occurs in approximately 50% of lesions, the irregular appearance of the growing melanoma may contrast strikingly w ith the more regularly pigmented and outlined residual naevus component.All patients with suspected malignant melanoma should have an excision biopsy of the lesion carried out with a margin of 1-2 mm of clinically normal skin.Incisional or punch biopsies should NOT be performed in suspected melanoma because of sampling error, because an inaccurate tumour thickness may be obtained due to biopsy trauma, and also because the overall shape and symmetry of the whole lesion is important to the diagnosis of melanocytic lesions. There is a theoretical risk of displacing melanoma cells deeper into the dermis.The essential pathological features of superficial spreading melanoma are the presence of a focus of malignant melanoma cells invading the dermis w ith areas of in situ malignant change in the adjacent epidermis.Melanocyte differentiation markersS100Gpl00/HMB-45typrosinaseMART-1/Melon-AHMW_MAAS100 is less specific than the other three, but highly sensitive and therefore is usually used in combination with at least one of the others.Invasive melanomas up to 2 mm thick may be safely treated with a minimal excision margin of 1 cm.In patients with thicker tumours, the recommended excision margin is 2 to 3 cm.