Dermoscopy of Uncommon Melanoma Variants—Perspective From the Pathologist

Abstract

The article by Pampena et al 1 describes 10 rare melanoma variants. Their systematic review highlights the challenging nature of diagnosing melanomas with atypical clinical and dermoscopic features, with a wide differential diagnosis that often includes nonmelanocytic tumors and inflammatory conditions.This systematic review also highlights the complex and evolving nature of melanoma classification, which has traditionally been based on histopathologic and clinical features but more recently also incorporates genomic alterations. 2,3 Many rare variants of melanoma have been described that often defy classification among the traditional major subtypes. By definition, these variants have atypical clinical or histopathologic features, and based on the current study, many may also exhibit unique dermoscopic patterns.The primary traditional subtypes of invasive melanoma include superficial spreading, nodular, lentigo maligna, and acrallentiginous melanoma. These longstanding groups exist to reflect differences in tumor progression and biological behavior based on clinical observations and distinct microscopic features. The characteristic dermoscopic features of these subtypes are well described. Because our understanding of the genetics of melanoma has markedly expanded over the last decade, melanoma subtype classification is in flux. The most recent edition of the World Health Organization Classification of Skin Tumours 2 presents a new classification scheme that attempts to incorporate genomic alterations with existing diagnostic criteria and histopathologic features to better reflect multiple unique tumor progression pathways beyond the conventional "big 4." Among the 10 uncommon variants in-