Invasive Melanoma Arising in a BAP1-Inactivated Melanocytic Tumor With NRAS Mutation: A Report of Exceptional Case With Emphasis on Its Genomic Features and Review of the Literature

BAP1-inactivated melanocytic tumor is a distinct entity with loss of BAP1 protein and epithelioid morphology. It shares histopathologic features with Spitz nevus and nevoid melanoma, and it can occur sporadically or with germline BAP1 predisposition syndrome. These lesions typically have tumor-infiltrating lymphocytes and infrequent mitoses. They are generally indolent, though melanoma can arise in both germline and sporadic cases. Most show BRAF V600E and BAP1 mutations. We describe four tumors in one patient diagnosed with BAP1-tumor predisposition syndrome (BAP1-TPDS): two invasive melanomas arising in BIMT and two BIMTs with uncertain malignant potential. Molecular analysis and fluorescence in situ hybridization (FISH) revealed BAP1 and NRAS mutations in melanoma and BAP1-inactivated melanocytic tumor components, with a gain of 6p25 (RREB1) in the melanoma component only. The patient completed pembrolizumab adjuvant therapy with no evidence of metastasis. This is a rare presentation of BIMT with BAP1 and NRAS mutations, absence of BRAF V600 mutation, and loss of BAP1 immunoreactivity in all lesional cells. Our case adds to the understanding of the histomorphologic and mutational spectrum in BAP1-inactivated melanocytic tumors.