Clinicopathologic features of incident and subsequent tumors in patients with multiple primary cutaneous melanomas.
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0.6-12.7% of patients with primary cutaneous melanoma will develop additional melanomas. Pathologic features of tumors in patients with multiple primary cutaneous melanomas have not been well described. In this large, international, multicenter, case-control study, we compared the clinicopathologic features of a subsequent melanoma with the preceding (usually the first) melanoma in patients with multiple primary cutaneous melanomas, and with those of melanomas in patients with single primary cutaneous melanomas.Multiple primary melanoma (cases) and single primary invasive melanoma (controls) patients from the Genes, Environment and Melanoma (GEM) study were included if their tumors were available for pathologic review and confirmed as melanoma. Clinicopathologic characteristics of invasive subsequent and first melanomas in cases and invasive single melanomas in controls were compared.A total of 473 pairs comprising a subsequent and a first melanoma and 1,989 single melanomas were reviewed. Forward stepwise regression modeling in 395 pairs with complete data showed that, compared with first melanomas, subsequent melanomas were more commonly contiguous with a dysplastic nevus, more prevalent on the head/neck and legs than other sites, and thinner. Compared with single primary melanomas, subsequent melanomas were more likely to be associated with a contiguous dysplastic nevus, more prevalent on the head/neck and legs, and thinner. The same differences were observed when subsequent melanomas were compared with single melanomas. First melanomas were more likely than single melanomas to have associated solar elastosis and no observed mitoses.Thinner subsequent than first melanomas suggest earlier diagnosis, perhaps due to closer clinical scrutiny. The association of subsequent melanomas with dysplastic nevi is consistent with the latter being risk factors or risk markers for melanoma.