[Abstract] Objective：To explore the clinicopathological features, immunophenotype, and molecular characteristics of sinonasal SMARCA4-deficient carcinoma with intracranial invasion. Methods：Retrospective analysis of the histological features, immunophenotype, and molecular alterations in a case of SMARCA4-deficient carcinoma invading intracranially from the sinonasal region, with clinicopathological characterization and literature review. Results：A 70-year-old male patient presented with a sinonasal tumor invading intracranially. Microscopically, the tumor cells were arranged in nests and solid sheets with focal necrosis. The tumor cells exhibited a high nuclear-to-cytoplasmic ratio, round to oval nuclei, and brisk mitotic activity, resembling large cell neuroendocrine carcinoma. Immunohistochemistry showed partial positivity for AE1/AE3 and Syn, loss of BRG1 expression, retained INI-1, and a Ki-67 proliferation index of 70%. Molecular testing revealed a nonsense mutation in SMARCA4 exon 8(c. 1252C＞T, p. Q418*)and a missense mutation in CTNNB1 exon 3(c. 134C＞T, p. S45F). Pan-cancer survival analysis revealed that the difference in outcomes between the SMARCA4/CTNNB1 co-mutation group and the SMARCA4- only mutation group was statistically significant(P ＜0.001). Conclusion：Sinonasal SMARCA4-deficient carcinoma is a rare and highly aggressive sinonasal cancer with non-specific histological features. SMARCA4/BRG1 immunohistochemical screening is crucial for early diagnosis, while next-generation sequencing(NGS)can provide more precise diagnostic information for patients.