[SWI/SNF complex-deficient sinonasal carcinomas: a clinicopathological analysis of 13 cases]

Objective: To investigate the clinicopathological features, immunophenotype and prognosis of SWI/SNF complex-deficient sinonasal carcinomas. Methods: The clinicopathological, immunohistochemical profiles of 13 SWI/SNF complex-deficient sinonasal carcinomas diagnosed at Xuanwu Hospital, Beijing, China between Januay 2019 and December 2024 were reviewed and followed up. Results: The patients' ages ranged from 33-81 years, median 59.0 (41.5, 64.5) years, including 10 males and 3 females. Imaging findings showed space-occupying lesions in the nasal cavity and sinuses. Microscopically, tumors predominantly exhibited invasive growth in medium-to-large nests or sheets, with relatively uniform morphology, mainly basaloid and/or small cells, while one recurrent case displayed epithelioid morphology. Focal necrosis was observed in 7 cases. Immunohistochemical results showed loss of SMARCA4/BRG1 in 7 cases, loss of SMARCB1/INI1 in 6 cases, and concurrent loss of SMARCA2 in 5 cases. CKpan was expressed to varying extent in all cases, 10 cases were EMA positive, and 5 cases were partially positive for p63/p40. Among neuroendocrine markers, 10 cases showed focal expression of syn or CgA. The Ki-67 proliferation index ranged from 40% to 90%. PD-L1 staining showed combined positive score (CPS) was ≥1 in 3 SMARCB1-deficient cases (CPS ranging from 2 to 3) and CPS <1 in the other 10 cases. Among the 13 patients, 2 were lost to follow-up, 6 died (postoperative survival: 1-25 months), and 5 remained alive, with the longest survival time of 130 months (follow-up range, 8-130 months). Conclusions: SWI/SNF complex-deficient sinonasal carcinoma is a rare undifferentiated malignancy in the head and neck, characterized by distinct pathological and molecular genetic features. SMARCA4-deficient and SMARCB1-deficient carcinomas both exhibit basaloid or small cell-like morphology. Compared to SMARCB1-deficient carcinomas, SMARCA4-deficient carcinomas show reduced expression of squamous cell markers but increased expression of neuroendocrine markers. The positive PD-L1 staining is more likely present in SMARCB1-deficient carcinomas than SMARCB4-dificient ones. Co-loss of SWI/SNF and SMARCA2 correlates with poorer prognosis. Comprehensive evaluation of histopathology, immunohistochemistry, and molecular genetics is critical for accurately diagnosing this rare entity.