Unclassified sclerosing malignant melanomas with AKAP9-BRAF gene fusion: a report of two cases and review of BRAF fusions in melanocytic tumors
The current classification of melanocytic tumors includes clinical, pathological, and molecular data. A subset of lesions remains difficult to classify according to these complex multilayer schemes. We report two cases of deeply infiltrating melanomas with a sclerosing background. The first case occurred on the back of a middle-aged man appearing clinically as a dermatofibroma. The architectural and cytological aspects resembled those of a desmoplastic melanoma but the strong expression of both melanA and HMB45, two stainings usually reported as negative in this entity, raised the question of an alternate diagnosis. The second case was a large, slowly growing, perivulvar tumor in a middle-aged woman. The morphology was complex with a central junctional spitzoid pattern associating an epidermal hyperplasia with large nests of large spindled melanocytes. The dermal component was made of deeply invasive strands and nests of nevoid unpigmented melanocytes surrounded by fibrosis; a perineural invasion was present at the periphery of the lesion. In both cases, aCGH found, among many other anomalies, a chromosomal breakpoint at the BRAF locus. RNA sequencing identified in both an AKAP9-BRAF gene fusion. A complementary resection was performed and no relapses have been observed in the respectively 15 and 6 months of follow-up. Both of these melanomas remained unclassified. We further review the variety of melanocytic tumors associated with such BRAF fusions.
KeywordsMelanocytic tumors Melanoma Desmoplastic stromal reaction BRAF fusion
Dr. Emilie Perron gratefully acknowledges the “Bourse McLaughlin du doyen de la Faculté de médecine de l’Université Laval” and the TEVA Innovation Canada fellowship grants.
Compliance with ethical standards
The study was conducted according to the Declaration of Helsinki and has been approved by the research ethics committee of the Centre Léon Bérard (Ref: L17-70).
Conflict of interest
The authors declare that they have no conflict of interest.
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