Sclerosing epithelioid fibrosarcoma.

We report the case of a 55-year-old woman who developed a mass in the soft tissue of the anterior right proximal thigh. Microscopic findings in the biopsy specimen supported the diagnosis of sclerosing epithelioid fibrosarcoma (SEF). This entity is part of a spectrum of lesions that includes low-grade fibromyxoid sarcoma (LGFMS) and hyalinizing spindle cell tumor with giant rosettes (HSCTGR). It shares with LGFMS occasional overlapping histopathologic features and immunopositivity for MUC4. Although FUS and CREB3L2 gene rearrangements, characteristics of LGFMS, have been found in hybrid tumors (those with features of both SEF and LGFMS) and in examples of LGFMS with relapses showing SEF morphology, it appears that EWSR1 and CREB3L1 rearrangements predominate over FUS and CREB3L2 rearrangements among "pure" SEF tumors. Recent information about SEF is briefly reviewed.