Squamous cell carcinoma is the most common sinonasal tract carcinoma, with varying histologic patterns and clinical behavior. Various genetic alterations have been described in sinonasal tumors, including deficiencies in the switch/sucrose nonfermentable complex and its subunits, such as SMARCB1/INI1. We present a metastatic poorly differentiated sinonasal squamous cell carcinoma with diffuse SMARCB1/INI1 loss, which raises important diagnostic considerations for this evolving tumor type.
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