Multimodal treatment of a low-grade Nasosinusal Sarcoma: Insights from a rare case

Biphenotypic sinonasal sarcoma (BSNS) is a rare, recently recognised malignant tumour of the sinonasal tract, characterised by distinctive biphenotypic myogenic and neural differentiation and frequently associated with the PAX3-MAML3 gene rearrangement. Its locally aggressive behaviour and proximity to critical structures pose significant diagnostic and therapeutic challenges. We report a case of a 59-year-old female presenting with a progressively enlarging intercanthal mass, ultimately diagnosed as BSNS with ethmoidal, orbital, and endocranial extension. Surgical resection was performed, including ethmoidectomy and removal of the frontal tumour component, achieving near-complete excision while preserving vital structures. Post-operative imaging revealed a small residual tumour in the left ethmoidal cells with extra-conical fat infiltration, necessitating adjuvant radiotherapy with a total dose of 70 Gy in 35 fractions. The treatment was well tolerated, with only mild acute side effects. At two-year follow-up, there was no evidence of local or loco-regional recurrence, highlighting the effectiveness of a combined modality approach in managing advanced BSNS. This case underscores the importance of a multidisciplinary strategy involving surgery and radiotherapy when complete resection is not feasible due to anatomical constraints. Clear patient counselling regarding recurrence risk and the necessity of regular long-term follow-up is essential to optimise outcomes. Our experience contributes to the limited literature on BSNS management, reinforcing current recommendations and advocating for further studies to establish standardised treatment protocols for this rare entity.