A 27-year-old female with sclerosing epithelioid fibrosarcoma of the left ethmoid sinus

Background: Sclerosing epithelioid fibrosarcoma (SEF) is a rare and poorly recognized variant of low-grade fibrosarcoma. SEF most often occurs in the soft tissue of the extremities and trunk. Treatment results and therapeutic options are poorly characterized. The head and neck are rare sites of occurrence and no study to date has described a case of SEF occurring in the paranasal sinuses. Case presentation: We report the case of a 27-year-old woman who presented with worsening left-sided nasal congestion. CT revealed a low-density mass occupying most of the left ethmoid sinus and protruding into the left nasal cavity and nasopharynx. Left nasal mass excision with pathology showed tumor with bland proliferation of ovoid to slightly spindled cells in a uniform distribution in collagenous stroma, indicative of SEF. Conclusions: SEF of the left maxillary sinus was treated by surgical excision followed by anterior skull base resection. Morphological characteristics played a greater role in diagnosing SEF than immunohistochemistry findings. While rare, SEF should be considered in the differential diagnosis of nasal cavity masses.