Seasonal variation in the incidence of cutaneous malignant melanoma: an analysis by body site and histologic type.

A seasonal analysis of the incidence of cutaneous malignant melanoma was conducted to investigate the degree to which the increased frequency of cases diagnosed in the summer may be due to an artifact of increased ascertainment. The monthly incidence of 13,151 microscopically-confirmed cases of cutaneous malignant melanoma diagnosed between 1973 and 1982 among white residents of nine regions in the United States served by population-based cancer registries participating in the Surveillance, Epidemiology, and End Results (SEER) program was evaluated for the presence of seasonal trends. Except for nodular melanoma, there was substantial seasonal variation in the incidence of all histologic types. For the two most common categories, superficial spreading melanoma and melanoma not further classified as to histology (of which the majority are likely to be superficial spreading melanoma), the peaks in incidence at body sites which are likely to experience seasonal changes in clothing (upper limbs, trunk, legs) occurred in the summer and were of similar relative size to the peaks, located in the spring, at sites which are likely to experience little variation in clothing during the year (head, face, and neck). A summer peak was also observed for Hutchinson's melanotic freckle melanoma of the head, face, and neck. The presence of seasonal variation in the incidence of superficial spreading melanoma of the head, face, and neck suggests that increased ascertainment cannot by itself account for seasonal variation in the incidence of superficial spreading melanoma of other parts of the body.