Abstract

Since first described by Wiesner et al, the recognition of BAP1 inactivated melanocytic tumors (BIMTs) has advanced the ability of pathologists to correctly categorize these unusual melanocytic neoplasms. A significant challenge remains, however, in distinguishing benign lesions from their malignant counterparts when atypical features are present. Herein, we present a series of cases of BIMTs ranging from atypical nevi to melanoma, their histopathologic features, and their cytogenetic landscapes as determined SNP array (OncoScan). All cases shared at least partial nuclear atypia, lack of morphological maturation, one or more dermal mitotic figures and/or noticeable Ki-67 labeling index. Detected cytogenetic abnormalities ranged from none (1 case), BAP1 locus only (9 cases), minor abnormalities in addition to BAP1 locus (3 cases), and complex abnormalities (2 cases). We also recognize that cytogenetic abnormality involving the BAP1 locus is not specific to the diagnosis of BIMTs; this abnormality was also detected in conventional melanoma (1 case), Spitz melanoma of childhood (1 case), blue nevus-like melanoma (2 cases) and a borderline tumor that could not be further classified (1 case). This work advances the ability of pathologists to recognize BIMTs as well as distinguish between their benign and malignant counterparts and adds the cytogenetic features of BAP1-inactivated melanoma to the existing body of research on this subject.

Financial Disclosure: No current or relevant financial relationships exist.