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Case Reports

Abstract

An 81-year-old male presented with a 1.5 cm irregular, multi-colored papule in the right periumbilical area. A shave biopsy was performed, revealing a predominantly dermal proliferation of nests and sheets of atypical, pleomorphic melanocytes without maturation. Pagetoid migration and ulceration were also noted in the overlying epidermis. Lesional cells demonstrated increased expression of PRAME and Ki-67 proliferation index. The diagnosis of ulcerated nodular melanoma was rendered, with a Breslow thickness of at least 5.8 mm and 30 mitoses per mm². A staging PET scan failed to show evidence of metastatic melanoma. Lymphoscintigraphy failed to reveal any draining nodal basin on the day of surgery (likely due to prior breast reduction); therefore, he proceeded with only a wide local excision. Histologic examination revealed residual melanoma with negative margins (final pT4bNXM0 Stage IIC melanoma). To explore possible targeted therapies, next-generation sequencing was requested. A catenin alpha-1 (CTNNA1)::BRAF fusion was discovered, in addition to a TERT promoter mutation (c.-124C>T) and Triple Wild-Type phenotype (TWT; lacking mutations in BRAF, NRAS, and NF1). While BRAF mutations are the most common somatic mutation seen in melanoma, gene fusions involving BRAF are rare in non-Spitz melanomas. CTNNA1, encoding alpha-1-catenin, a critical element of cadherin-mediated cell adhesion, has not been previously described as a fusion partner with BRAF in any melanoma. Herein, we report a novel BRAF fusion partner in a patient with TWT nodular melanoma. This case contributes to our expanding knowledge of the molecular landscape of melanoma, highlighting a unique molecular alteration with potential therapeutic implications.