Micro-nevi in peri-tumoral skin of cutaneous melanoma and basal cell carcinoma

Abstract

Background: Harboring many melanocytic nevi is a risk factor for melanoma. The prevalence of micro-nevi, melanocytic nevi that can only be detected microscopically, has been studied scarcely and the significance is unknown. Objectives: To systematically analyze the presence of micro-nevi in cutaneous excisions from cutaneous melanoma and basal cell carcinoma to achieve an insight in the density of micro-nevi per mm peri-tumoral skin. Also to speculate in the relevance and significance of micro-nevi for evolving melanoma at the same anatomical site. Methods: We re-examined histologically peri-tumoral skin of primary and re-excised melanomas and primary excisions of basal cell carcinomas for comparison. The size of a micro-nevus was defined to a diameter < 2 mm, of either a junctional, compound or intradermal nevus. Results: 104 melanoma and 208 basal cell carcinoma cases were microscopically re-examined. In the melanoma group 6 micro-nevi were found. The sum of the peri-tumoral skin was 1768 mm, giving a density of 1 nevus per 295 mm. In the basal cell carcinoma group 5 micro-nevi were found. The sum of the peri-tumoral skin was 1370 mm, giving a density of 1 nevus per 274 mm. No difference in the density of micro-nevi in the two groups of skin cancer was found. Conclusions: The significance of these micro-nevi remains unclear. The aim with this study is to draw attention to the existence of micro-nevi and further studies are needed to determine the significance of the presence of micro-nevi.