Sun exposure and host phenotype as predictors of cutaneous melanoma associated with neval remnants or dermal elastosis

Abstract

Recent research suggests that cutaneous melanomas may arise through 2 distinct pathways, characterized by chronic sun exposure on one hand and nevus‐prone phenotype of the host on the other. Two histological characteristics of melanoma consistent with these divergent origins are dermal elastosis in adjacent skin and neval remnants contiguous with the tumor, respectively. To further explore causal heterogeneity in melanoma, we compared sun exposure histories and phenotypic characteristics among a population‐based sample of patients newly diagnosed with cutaneous melanoma with and without contiguous neval remnants or dermal elastosis. Tissue blocks were obtained for 141 patients: 53 with superficial spreading melanoma (SSM) of the back, 42 with SSM of head and neck (H & N), and 39 and 7 with lentigo maligna/lentigo maligna melanoma (LM/LMM) of the H & N and back, respectively. Melanomas of the H & N were less likely than those on back to have neval remnants (adjusted OR 0.6, 95% CI 0.3–1.4), but were significantly more likely to have dermal elastosis (adjusted OR 9.3, 95% CI 3.5–25). In site‐specific analyses, we found that H & N melanomas with neval remnants were more likely than those without neval remnants to arise in people with more than 60 nevi (adjusted OR 2.1, 95% CI 0.3–14.3), but were less likely to arise in those with more than 20 actinic keratoses. Less marked associations were observed for melanomas of the back. High levels of sun exposure strongly predicted dermal elastosis for H & N melanomas (OR 22.5, 95% CI 2.1–245), but not for melanomas of the back (OR 2.1, 95% CI 0.4–11). We conclude that melanomas with different histologic characteristics have different risk factor profiles, particularly on the head and neck. These data accord with the hypothesis that melanomas arise through different causal pathways.