Targeted next-generation sequencing reveals activating CTNNB1 mutations in SMARCA4/BRG1-deficient sinonasal carcinomas: a report of two new cases and a brief review of the literature with an emphasis on histogenesis.

SMARCA4/BRG1 is a catalytic subunit of the SWItch/sucrose non-fermentable (SWI/SNF) complex and its inactivation is known to drive a variety of cancers across different organs. SMARCA4/BRG1-deficient carcinoma is a relatively new entity in the sinonasal region, and a comprehensive molecular investigation of the underlying genetic abnormalities is largely lacking. In this study, we report two new cases of SMARCA4/BRG1-deficient sinonasal carcinoma with targeted next-generation sequencing analysis, both of which revealed activating mutation of CTNNB1 in addition to somatic loss-of-function mutation of SMARCA4, providing further insights into its tumorigenesis and theoretical basis for the potential future targeted therapy. Activating CTNNB1 mutations in our cases may provide further evidence that SMARCA4-deficient sinonasal carcinoma, sinonasal teratocarcinosarcoma, and olfactory carcinoma are genetically closely related lesions, as recently proposed in the literature.