Melanoma of the skin and laterality

We were intrigued by the study of Butler and Fosko reporting a left-sided predominance of skin cancers, particularly among men.1 However, findings for melanoma were inconclusive due to the limited number of cases available for analysis. Therefore, using the large numbers of cases available in the Surveillance, Epidemiology and End Results (SEER) Program, we assessed the incidence of melanoma diagnosed among White residents of 12 SEER registry areas during 1992–2006.2 Histology and topography information are classified according to the International Classification of Diseases for Oncology, third edition.3 Age-adjusted incidence rates (IRs) and IR ratios (IRRs) were estimated for all cutaneous (C-440-449) melanomas (M-8720-8790) for sites with more than 70% of cases having specified laterality: eyelid (n=777; 99%), ear (n=4,772; 99%), other face (n=19,273; 91%), trunk (n=29,329; 71%), upper extremity (32,237; 99%), and lower extremity (23,679; 99%). Among males, incidence of left-sided melanoma was significantly higher than right-sided melanoma across all skin sites, ranging from 7–26% (Table 1). Among women, significantly higher IRs for left-sided melanoma were limited to the face, and upper and lower extremities, although left-sided lesions predominated at all sites (IRRs 1.03–1.15). A left-sided predominance was observed for in situ and invasive melanoma at all sites among males, in contrast to women who had nearly equal or a slight right-sided predominance for in situ melanoma of the ear and trunk and invasive melanoma of the eyelid. Except for eyelid melanoma among older women, left-sided melanoma predominated at all sites among younger (