[A cutaneous lesion of the axilla: an (un)common diagnosis]

A 21-year-old female presented with a 1 cm red, polypoid cutaneous tumor near the axilla that was surgically excised. Histomorphology revealed a subepithelial tumor with features suggestive of a granular cell tumor; however, immunohistochemistry for S100 and SOX10 was negative. Further analysis showed immunohistochemical ALK positivity, and Archer-based molecular testing identified a KLC1-ALK fusion (KLC1 exon 3-ALK exon 20). These findings supported the diagnosis of a cutaneous non-neural granular cell tumor, a rare cutaneous neoplasm that mimics conventional granular cell tumors histomorphologically but lacks their typical immunophenotype and commonly harbors ALK fusions.