Striking increase of thin melanomas contrasts with stable incidence of thick melanomas.

OBJECTIVE The aim of this study was to analyze the temporal evolution of melanoma incidence in the department of the Bas-Rhin, France, and to study the evolution of tumor thickness. DESIGN Retrospective study including all histologically proven melanomas recorded at the cancer registry of the department of the Bas-Rhin between January 1980 and December 1992 and at the Cutaneous Histopathology Department of the University Hospitals, Strasbourg, between January 1980 and December 1997. SETTING Population-based cancer registry and academic cutaneous histopathology department. PATIENTS A total of 1254 patients with histologically proven melanomas. INTERVENTION None. MAIN OUTCOME MEASURES Temporal evolution of melanoma incidence and tumor thickness. RESULTS The mean (SD) and median tumor thicknesses were 1.48 (1.59) mm and 0.87 mm, respectively, and they decreased during the study period. The increase in the number of melanomas was mainly related to an increase of superficial spreading melanomas in both sexes. The number of intermediate melanomas (1-2 mm) in both sexes and the number of melanomas with a Breslow index between 2 and 4 mm in women increased only slightly. The number of melanomas with a Breslow index greater than 2 mm in men and greater than 4 mm in women remained stable during the reference period. CONCLUSION A striking increase in incidence of thin melanomas contrasts with a stable incidence of thick melanomas.