Biphenotypic Sinonasal Sarcoma with Focal Rhabdomyoblastic Differentiation: Case Report of a Newly Described Malignancy with a Review of the Literature

Background Sinonasal sarcomas are rare, comprising less than 10% of all head and neck sarcomas. As a group, these malignancies encompass a wide variety of tumor types, making correct histological classification difficult. However, accurately classifying histology informs prognosis and drives distinct and highly varied treatment paradigms. Adding to clinical complexity are newly identified entities including the recently described biphenotypic sinonasal sarcoma with focal rhabdomyoblastic differentiation (BSNS).

Case We present a case of a 53-year-old man presenting with 4 months of unilateral nasal obstruction and epiphora. Clinical examination showed an expansile lesion arising from the left middle meatus. Imaging showed complete opacification of the left frontal sinus with erosion of the ipsilateral lamina papyracea and central cranial base. Office biopsy revealed a spindle cell neoplasm most consistent with a benign schwannoma. The patient was taken to surgery where initial frozen section pathology was again consistent with schwannoma. Intraoperatively, the tumor was found to involve the left periorbita and, to preserve orbital integrity, a near-total resection was pursued given the presumed benign nature of the tumor. Final pathology returned consistent with BSNS. The patient was subsequently taken for oncologic resection of the remaining tumor and received adjuvant external bean radiotherapy for definitive treatment.

Discussion Both histologic classification and optimal clinical management strategies of newly described sinonasal sarcomas, including BSNS, are not well defined. Indeed, a significant portion of sinonasal sarcomas remains unclassified. Individually, sarcomas of the head and neck portend widely varying prognoses, dictated in large part by histologic class. While rhabdomyosarcomas often confer a dismal prognosis, BSNS may represent a less aggressive entity appropriate for de-escalation of therapy. We discuss the clinical features of this newly described malignancy with review of published case series and efforts to characterize the histopathologic features of this tumor. Evidence for a less aggressive treatment approach is reviewed. Given the rarity of this novel tumor type, further study is required to establish both diagnostic histopathologic and clinical management guidelines.