Abstract

BRCA-1 associated protein (BAP1) tumor predisposition syndrome is described in the literature as a syndrome with increased risk of cutaneous melanocytic tumors and solid organ malignancies. BAP1 gene encodes a tumor suppressor protein on chromosome 3p21. BAP1 cutaneous lesions can exhibit a range of morphologies including spitzoid, rhabdoid, epithelioid and biphasic patterns. Cutaneous melanoma cases have been reported in families with BAP1 germline mutations. Nuclear loss of BAP1 staining on immunohistochemistry (IHC) is essential for the diagnosis; however, several confounders can interfere with interpretation, such as background cytoplasmic staining. We report a case of a 66 year-old female with a past medical history of BAP1 tumor predisposition syndrome(heterozygous pathogenic variant in BAP1), and multiple solid organ malignancies who presented to dermatology for a hard, painful, mobile scalp lesion. Histopathologic examination of the scalp punch biopsy showed a nodular invasive melanoma, Clark’s Level IV, Breslow thickness 6mm, and mitoses 2/mm2. IHC staining showed retained BAP-1. We describe a case of cutaneous melanoma in a patient with BAP1 tumor predisposition syndrome with retained BAP1 staining on IHC. A rare case of BAP1-inactivated melanocytic tumor (BIMT) with retention has been described in the literature. The authors' subsequent molecular analysis showed a heterozygous loss of the BAP1 locus by chromosomal micro-array and a suspected pathologic variant by sequencing. Melanoma has key histologic characteristics that help to distinguish it from cutaneous BIMT. In cases where histology favors BIMT, IHC may be helpful; however, cytoplasmic staining or retained nuclear epitope recognition may confound interpretation.

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