Site distribution of malignant melanoma.

In a continuous series of 300 patients with cutaneous malignant melanoma the site of the primary lesion was recorded, and incidence rates per unit area of skin were calculated. These rates were high for the face, back and upper arm and low for the abdomen, buttocks, forearm and hand for both sexes. Rates for the leg were high for the women but low for the men. Tumours on the back were evenly distributed among the men but occurred less frequently on the lower back among the women. In general, sites that were usually covered by clothing had lower rates than those usually exposed, with the exception of the forearms and hands. No relation was seen between tumour site and age, sex, depth of invasion or month of diagnosis. Superficial spreading and nodular melanomas did not differ in their site distribution. Incidence rates per unit area at different ages were estimated for sites grouped by their degree of usual exposure: while the rates for unexposed sites were low, those for usually or intermittently exposed sites were higher and similar to each other.