Abstract
Lentiginous dysplastic nevus of the elderly (LDN), also known as atypical lentiginous nevus, first was characterized by Kossard in 1991 as a distinctive pigmented lesion, simulating melanoma and occuring on intermittently sun-exposed skin. It has since been neglected and often confused with a lentiginous melanoma variant with different clinicopathologic characteristics. We aimed to confirm LDN as a distinct category and further define its characteristics. A prospective study was conducted over 1.5 years, collecting cases aligned with the original description of LDN, with special emphasis on cases possessing findings conventionally associated with melanoma. Various characteristics were evaluated, including clinicohistopathologic features, immunohistochemistry (IHC), FISH, TERT promoter mutation analysis, and BRAF V600E status. Our findings in > 80% cases revealed a higher incidence of melanoma-associated features compared to previous descriptions, including intra-lentiginous growth, pagetoid spread, host response, prominent nucleoli and pleomorphism. However, consistent features of benignity were also observed, most notably small size, symmetry and a previously undescribed, but remarkable tendency to end in single cells with a distinctive pattern of abrupt termination. PRAME IHC was consistently negative, very useful in facilitating recognition of these lesions. Our observations expand the histopathologic spectrum of LDN to include several features once thought to indicate progression to melanoma. Nevertheless, the presence of important benign findings, negative adjuvant testing results, and favorable clinical follow-up support LDN as a distinct entity. This study provides evidence for the existence of LDN as a distinct nevus variant and aids in its differentiation from melanoma. The refined understanding of LDN’s defining characteristics