Epithelioid Fibrous Histiocytoma With Abundant Multinucleated Giant Cells: Report of 3 Cases of an Unusual Variant With Predilection for Acral Sites.

Epithelioid fibrous histiocytoma (EFH) is a rare, benign cutaneous neoplasm, thought to be distinct from benign fibrous histiocytoma because of its characteristic anaplastic lymphoma kinase (ALK) gene rearrangements. This article presents 3 cases of EFH with unusual multinucleated giant cells, all located on acral sites. The patients, 2 women and 1 man, ranged from 24 to 63 years of age. Histopathologically, these cases exhibited well-circumscribed lesions in the dermis, composed of sheets of epithelioid cells with abundant eosinophilic cytoplasm and round nuclei within a fibrous stroma. Notably, numerous multinucleated giant cells were present, all showing ALK positivity. Clinical follow-up, ranging from 3 to 120 months, revealed no recurrence, reinforcing the benign nature of EFH. These findings highlight the importance of distinguishing EFH from other cutaneous epithelioid neoplasms with multinucleated giant cells. The presence of ALK rearrangement serves as a critical diagnostic marker. This case series expands the histopathologic spectrum of EFH and emphasizes the need for awareness of its diverse presentations to avoid misdiagnosis.