Context.—: Biphenotypic sinonasal sarcoma (BSNS) is a rare, slow-growing soft tissue sarcoma of the sinonasal tract, typically presenting with nonspecific obstructive nasal symptoms. Although recurrences are common, no metastases have been reported, and only 1 patient has died of disease thus far. It characteristically demonstrates rearrangements of PAX3 with multiple fusion partners, the most common of which is MAML3.
Objectives.—: To highlight the most important diagnostic features, including morphologic, immunohistochemical, and molecular findings, and to provide comparisons to other entities in the differential diagnosis. We also aim to provide a summary of the clinical features and outcomes in cases reported to date.
Data sources.—: Recently published literature encompassing BSNS and its synonym, low-grade sinonasal sarcoma with neural and myogenic differentiation.
Conclusions.—: BSNS is a sinonasal tumor that is important to recognize because its biologic behavior differs from most of the entities in the differential diagnosis. The diagnosis can typically be rendered through a combination of morphology, immunohistochemical stains, and ancillary testing for characteristic PAX3 rearrangements.