SMARCB1-Deficient Sinonasal Carcinoma: A Case Report and Discussion of the Clinical Implications

Abstract

Objective: SMARCB1-deficient sinonasal tract carcinomas are an emerging subset of rare tumors recently described in the literature, with less than 100 reported cases. Given the aggressive nature of this tumor, timely diagnosis is especially important. We present a case report of a SMARCB1-deficient carcinoma of the sinonasal tract. Methods: Case report with review of the literature. Results: The patient was a 53-year-old male with computed tomography (CT)-proven mass of the right ethmoid and sphenoid sinuses. Rigid nasal endoscopy revealed a purple mass completely obstructing the right nasal cavity that extended inferiorly from the posterior ethmoids and sphenoid sinuses. Initial biopsy in the emergency room was nondiagnostic due to extensive tumor necrosis. Magnetic resonance imaging (MRI) revealed T2 hypointense enhancing mass centered in the right posterior ethmoids with invasion into the right orbital apex, classifying it as a T4b tumor. The patient underwent repeat biopsy with frozen section and tumor debulking. Immunohistochemical analysis of subsequent biopsy revealed complete loss of INI-1 and negative staining for other pertinent markers, alluding to the diagnosis of SMARCB1-deficient sinonasal tract carcinoma. Conclusion: Tumor necrosis may be problematic in obtaining a diagnosis for SMARCB1-deficient sinonasal carcinomas. Thus, sampling various regions of the tumor during initial biopsy can prevent delays in diagnosis and treatment.