Background It has been suggested that the incidence of thin melanomas but not of thick tumours is rising in fair-skinned populations, although the reason for this discrepancy is not understood.
Objectives To describe temporal trends in melanoma epidemiology in a limited part of France in order to confirm this observation and to provide an explanation.
Methods This is a retrospective population- and academic centre-based study in which all melanomas diagnosed in the department of the Bas-Rhin, France between January 1980 and December 2004 were included.
Results The study included 2094 melanomas diagnosed in 2020 patients. There was a steady increase in incidence of thin (< 1 mm) melanomas, mainly located on the trunk, and to a lesser extent in the head and neck region, in both sexes, and of intermediate (1–2 mm) melanomas in men. The incidence of intermediate melanomas in women and of thick (> 2 mm) melanomas, as well as mortality related to melanoma, remained stable. There was a steady decline of mean and median Breslow thickness. The 12 months median delay to diagnosis of thick tumours was significantly shorter than the 24 months delay to diagnosis of thin tumours.
Conclusions Temporal trends suggest the existence of three unrelated types of melanoma: type I, thick melanomas, with stable incidence; type II, thin melanoma with a steady and important increase in incidence, mainly located on the trunk; and type III, melanoma with a slower increase in incidence, mainly located on the head and neck region.