Biphenotypic sinonasal sarcoma with diffuse infiltration and intracranial extension: a case report

Biphenotypic sinonasal sarcoma (BSNS) is a new entity which is a low-grade spindle cell sarcoma with neural and myogenic differentiation and recurrent PAX3 rearrangement. Herein, we present one case of BSNS with diffuse infiltration. We analyzed its clinicopathological features and differential diagnosis. In conclusion, BSNS is a low-grade spindle cell sarcoma. The differential diagnosis includes schwannoma, malignant peripheral nerve sheath tumor, synovial sarcoma, and spindle cell rhabdomyosarcoma. As for the prognosis, BSNS commonly recurs and rarely metastasis. However, it may invade extensively and results in poor prognosis.