| Abstract: | Germline mutations in BRCA1‐associated protein 1 (BAP1) are associated with several neoplasms, including BAP1‐inactivated melanocytic tumors (BIMTs). BIMTs are classically described as biphenotypic melanocytic proliferations with BAP1‐deficient large epithelioid and rhabdoid melanocytes showing various degrees of cytologic atypia. This morphology has been traditionally classified as “spitzoid” despite the various differences between these lesions and the more classic Spitz nevi. Herein, we report a case of an otherwise healthy 11‐year‐old female patient with a family history of several malignancies who presented with multiple pink to brown papules. Histologic and immunohistochemical evaluation identified three lesions with loss of nuclear BAP1 staining. The histologic spectrum of these lesions included junctional spitzoid cells within a triphenotypic proliferation and a separate lesion composed entirely of dermal small to medium‐sized epithelioid melanocytes with maturation. BAP1 gene sequencing revealed a germline frameshift pathogenic BAP1 mutation, denoted c.1717delC. This case provides further evidence that not all BIMTs conform to classic morphological criteria and that the morphologic spectrum includes lesions resembling conventional nevi. As BIMTs can serve as an early marker of the BAP1 hereditary tumor predisposition syndrome, we believe a need exists for a more comprehensive combined clinical and pathological approach for BIMT identification. |
