Multifocal Epithelioid Hemangioma With FOSB Overexpression.

Abstract

Epithelioid hemangioma (EH) is a benign vascular tumor that most commonly arises on the skin but may also occur in other anatomical locations, including deep soft tissue, bone, visceral organs, penis, and mucosal sites. A hallmark of EH is overexpression of FOS and FOSB, often resulting from various gene fusions. However, cases in the literature describe diverse mechanisms of FOS/FOSB expression across EH subtypes, suggesting that these variants may be driven by different molecular pathways. We present a case of an 83-year-old male with multiple well-circumscribed lesions on the right buttock and proximal thigh, demonstrating a multicentric growth pattern with satellitosis and FOSB positivity on immunohistochemistry. To our knowledge, this is one of the few reported cases of multifocal EH demonstrating FOSB positivity, further supporting the emerging view that multifocal EH may represent a true neoplastic process rather than a reactive phenomenon.