Clinical Question: Has the incidence of skin melanoma increased?
Study Design: Ecologic
Synopsis: The incidence of skin melanoma is now six times higher than in 1950. The researchers conducting this study attempted to determine if the true incidence is rising or if the increase is caused by an increased biopsy rate. Histologic diagnosis of melanoma is difficult, and several studies have shown that pathologists cannot agree on which samples are really melanoma (Pathology as art appreciation: melanoma diagnosis.http://www.jr2.ox.ac.uk/bandolier/band37/b37-2.html). This study compared skin biopsy rates for patients older than 65 years with the incidence of melanoma over five years in nine geographic areas in the United States. Over the five years, the number of biopsies in this age group increased 2.5-fold, from one out of 35 to one out of 14 persons. The incidence of melanoma increased 2.4-fold, from one out of every 2,222 persons to one out of every 925 persons. Despite this increase in diagnoses, mortality caused by melanoma changed little. These data suggest that the increase in melanoma diagnoses is simply because more lesions are being biopsied that would not have been biopsied in the past.
Bottom Line: This study provides preliminary evidence that the incidence of melanoma is increasing because skin lesions are being biopsied and not because of factors such as skin burns and holes in the ozone layer. (Level of Evidence: 2c)