Track: Clinical Studies

Abstract:

Sclerosing nevi with pseudomelanomatous features (SNPF) are a rare subset of melanocytic nevi that can mimic melanoma, both clinically and histologically. Previous studies have shown that SNPF lacks PRAME expression. To our knowledge, there is no molecular characterization of these unusual and diagnostically challenging lesions. The objective of this study was to explore the molecular landscape of SNPF to confirm the entities’ classification as benign nevi. Retrospective review of a single institution’s pathology archives from 2004-2024 using key search terms “sclerosing” and “pseudeomelanomatous” identified nine cases of SNPF. Molecular alterations in the cases were assessed via next-generation sequencing using a solid tumor panel following microdissection. Nine (n=9) SNPFs were identified with a mean patient age of 42 (range 25-65). Lesions were most commonly found in the back/flank (n=6), then abdomen/chest (n=2), and ankle (n=1). All lesions presented as irregular macules with varying pigmentation, clinically concerning for atypical nevi versus melanoma. All cases had negative or weak PRAME expression (9/9). Molecular analysis successfully characterized 8/9 of the cases. All successfully analyzed cases had BRAF V600E (c.1799T>A) alterations (8/8), with no other mutations of significance or copy number variations. Overall, this study represents the first reported molecular analysis of SNPFs, which are enriched for BRAF V600E mutations and otherwise show a benign molecular profile.

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Amy Guimaraes-Young