SWI/SNF-Deficient Sinonasal Carcinomas: A Retrospective Case Series of 17 Patients from a Single Institution

Objectives: We aimed to characterize the clinicopathologic features, treatment, and outcomes of three types of Switch/Sucrose Nonfermentable (SWI/SNF)-deficient sinonasal carcinomas (SDSCs), thereby expanding the spectrum of these rare entities and facilitating early diagnosis. Methods: We designed a retrospective single-center case series to analyze the clinicopathological features of 17 patients with SMARCB1-deficient sinonasal carcinoma (n = 10), SMARCA4-deficient carcinoma (n = 6) and SMARCA4-deficient sinonasal teratocarcinosarcoma (TCS) (n = 1) treated between 2018 and 2025, and reviewed the relevant literature. Results: The cohort included 14 males and 3 females, aged 26 to 69 years (mean, 47 years). SMARCB1-deficient sinonasal carcinomas predominantly involved the ethmoid sinus (6 of 8 patients), presenting epistaxis (7 of 10 patients), nasal obstruction (5 of 10 patients), and ocular symptoms (4 of 10 patients). SMARCA4-deficient sinonasal carcinomas mainly arose in the nasal cavity (3 of 4 patients), characterized by nasal obstruction (4 of 6 patients), and epistaxis or purulent rhinorrhea (4 of 6 patients); ocular symptoms were less common (2 of 6 patients). The TCS patient had left nasal cavity and ethmoid involvement with nasal obstruction and purulent rhinorrhea. Most patients presented with advanced-stage disease (T4a, n = 9), with skull base (n = 6), and orbital (n = 3) involvement. Histologically, immunohistochemical analysis confirmed complete SMARCB1 or SMARCA4 loss (complete in carcinomas and partial in TCS), diffuse CK positivity, and high Ki-67 indices. Treatment modalities included: chemotherapy and immunotherapy without surgery (n = 2), radical surgery with adjuvant chemoradiotherapy and immunotherapy (n = 2), radical surgery with chemoradiotherapy (n = 9), postoperative radiotherapy alone (n = 3), and non-radical surgery with chemoradiotherapy (n = 1). At a median follow-up of 19 months (range, 8-57 months), 2 patients were lost to follow-up, 3 died, 2 had persistent disease, and 10 remained disease-free. Conclusions: SDSC is an aggressive tumor with male predominance and advanced-stage presentation. Early recognition and appropriate immunohistochemical evaluation are essential for timely diagnosis and management. Prospective studies of novel targeted and immunotherapeutic strategies are warranted.