Interesting overlooked findings in melanocytic nevi

José Cândido Caldeira Xavier-Júnior,Solange Correa Garcia Pires D’Ávilla,Juliana Polizel Ocanha-Xavier,Deolino João Camilo-Júnior,Neivio José Mattar

doi:10.1186/s42047-019-0044-9

Abstract

Since histological analysis is the gold standard for melanoma diagnose, to understand possible findings in nevi is the first step to avoid diagnostic errors. The aim of this paper is to describe several histological features that can be found in nevi and may be misunderstood or overlooked. Histological findings were organized into two groups: 1- adaptive findings (neurotization, sebaceous alteration, adipose metaplasia, amyloid deposition and calcifications, pseudovascular lacunae), 2- findings that can occasionally be associated with malignancy (suspicious for angiolymphatic invasion, perineural infiltration, deep mitosis, muscle infiltration). Each finding by itself does not mean that lesion is malignant. We have selected 13 cases of benign intradermal or compound melanocytic nevi excised for aesthetical purposes from our collection to illustrate possible overlooked findings in melanocytic nevi.

Highlights

Despite melanocytic nevi are very frequent in daily practice, differential diagnose with melanoma can be tough sometimes
Cases with neural metaplasia are rich in type C cells
Most frequently that alteration is found with adipocyte metaplasia

Summary

Introduction

Despite melanocytic nevi are very frequent in daily practice, differential diagnose with melanoma can be tough sometimes. In this context, not common features can be challenging for Pathologists that are not used to them (Fernandez-Flores and Cassarino 2016). We might not forget, when a nevus cannot be characterized it might be a melanoma (Massi and LeBoit 2014). According to the World Health Organization (WHO) book about the classification of skin tumours, the most important differential diagnosis of melanocytic nevi is melanoma. This diagnose is based on clinical, dermatological and histological criteria. On a histological basis the following criteria are analyzed: symmetry, circumscription, ulceration, cellularity, pagetoid scatter, cytological atypia, mitotic activity, failure of cellular maturation, lymphovascular and perineural invasion (Edited by Elder et al 2018)

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