Biphenotypic sinonasal sarcoma – A diagnostic conundrum

Biphenotypic sinonasal sarcoma (BSNS) is a rare, low-grade soft-tissue sarcoma of the sinonasal tract, characterized by the presence of both mesenchymal and epithelial elements. This dual differentiation makes its diagnosis challenging, as it can mimic other sinonasal lesions, such as rhinosporidiosis and nasal polyps. We present the case of a 38-year-old male with a 9-month history of recurrent right-sided nasal bleeding. Clinical examination revealed a pinkish, polypoidal mass attached to the septum and middle turbinate. A provisional diagnosis of rhinosporidiosis was considered, but radiological imaging showed a well-circumscribed soft-tissue mass within the nasal cavity and ethmoid sinuses. Surgical excision of the mass was performed, and histopathological examination revealed a biphenotypic tumor with both mesenchymal and epithelial components, confirming the diagnosis of BSNS. Immunohistochemistry further supported the diagnosis, with the tumor cells testing positive for both mesenchymal (vimentin) and epithelial (cytokeratin) markers. The patient had an uneventful postoperative recovery and was discharged with follow-up care for monitoring recurrence. Although BSNS is rare, it should be considered in the differential diagnosis of sinonasal masses, especially when clinical and radiological findings suggest a benign lesion, as its presentation can closely mimic more common, noncancerous conditions. Early diagnosis and complete surgical excision are essential for favorable outcomes.