Epithelioid Fibrous Histiocytoma With Giant Cells and VCL-Anaplastic Lymphoma Kinase Fusion: A Diagnostic Challenge

Epithelioid fibrous histiocytoma (EFH) is a rare condition historically considered a morphologic variant of benign fibrous histiocytoma. However, recent molecular studies have shown that EFH is characterized by anaplastic lymphoma kinase gene rearrangements, which are absent in benign fibrous histiocytoma. In this case report, we describe a case of EFH in a young woman, which presented a histopathologic diagnostic challenge due to an exuberant giant cell proliferation with intervening monocytic cells, a feature not typically seen in EFH. Molecular workup revealed an anaplastic lymphoma kinase rearrangement, allowing for a diagnosis of EFH to be made.