SMARCB1缺陷型鼻腔鼻窦癌（SWI/SNF-related ，matrix-associated， actin-dependent regulator of chromatin， subfamily B， member 1-defcient sinonasal carcinoma， SDSC）是头颈部罕见的高侵袭性肿瘤占原发性鼻腔鼻窦癌的2.7%到7.0%，发病年龄跨度广，临床表现缺乏特征性，组织形态学与多种头颈部恶性肿瘤相似，病理诊断极具挑战性。本文报道广州市第一人民医院收治的2例SDSC患者，病例1（75岁女性）为SMARCB1（integrase Interactor 1，INI-1）伴SMARCA2（SWI/SNF-related， matrix-associated， actin-dependent regulator of chromatin， subfamily A， member 2）（brahma homolog，BRM）表达共缺失，肿瘤主要位于右侧上颌窦及鼻腔；病例2（60岁男性）仅SMARCB1（INI-1）表达缺失，肿瘤主要位于左侧后组筛窦。组织学上，2例都以基底样细胞为主，散在少量核偏位的浆细胞样/横纹肌样细胞，前者伴有大片肿瘤坏死，仅残留少许肿瘤组织。2例患者确诊时临床分期均为cT₄N_xM₀。经随访观察，病例1行2个周期的诱导化疗联合免疫治疗，于诊断后3个月死亡；病例2行肿瘤扩大切除术联合术后辅助治疗，于诊断后12个月死亡。对比2个病例，SMARCB1（INI-1）和SMARCA2（BRM）表达共缺失的病例，在形态学上伴有更显著的肿瘤坏死，生存时间更短。结合文献报道，国内外数据库搜索，共计报道236例SDSC，发病年龄25~86岁，男女比例为（5∶3）~（8∶3），SMARCBI（IN1-1）和SMARCA2（BRM）表达共缺失者4例（4/236）。分析文献，尚无充分的数据表明SMARCB1（INI-1）和SMARCA2（BRM）表达共缺失的病例具有更差的生存预后。SDSC患者的总体预后较差，目前尚无标准治疗方案。形态学检查联合SMARCB1（INI-1）免疫组化检测是明确诊断的关键，SWI/SNF复合物成员蛋白的联合检测有助于共缺失病例的检出。共缺失的病例少见，目前其对生存预后分析的意义尚不明确，需积累更多临床经验。

SMARCB1(SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily B, member 1)-deficient sinonasal carcinoma (SDSC) is a rare and highly aggressive malignant neoplasm of the head and neck region, accounting for 2.7% to 7.0% of primary sinonasal carcinomas. It exhibits a broad age distribution, non-specific clinical manifestations, and histomorphological features that closely mimic various other head and neck malignancies, posing significant diagnostic challenges for pathologists. This report details two SDSC cases treated in the Department of Patho-logy, Guangzhou First People's Hospital. Case 1 was a 75-year-old female who demonstrated combined loss of expression of SMARCB1 (Integrase Interactor 1, INI-1) and SMARCA2(SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 2) (Brahma Homolog, BRM) proteins. The tumors were mainly located in the right maxillary sinus and nasal cavity. Case 2 was a 60-year-old male who exhibited loss of SMARCB1 (INI-1) expression only. The tumors were located in the left posterior ethmoid sinus. Histologically, both cases were predominantly composed of basaloid cells, interspersed with a minor population of cells exhibiting plasmacytoid/rhabdoid morphology characterized by eccentric nuclei. Case 1 featured extensive geographic tumor necrosis, with only scant residual viable tumor tissue. The clinical stage of both cases was cT₄N_xM₀ at the time of diagnosis. Follow-up: Case 1 received two cycles of induction chemotherapy combined with immunotherapy and died 3 months post-diagnosis. Case 2 underwent extended tumor resection followed by adjuvant therapy and died 12 months post-diagnosis. Comparative analysis revealed that the case with co-loss of SMARCB1 (INI-1) and SMARCA2 (BRM) expression was accompanied by more significant tumor necrosis morphologically and had a shorter survival time. According to literature and database searches worldwide, a total of 236 SDSC cases were reported, with an age range of 25-86 years and a male-to-female ratio of approximately 5:3 to 8:3. Among them, four cases (4/236) showed co-loss of SMARCB1 (INI-1) and SMARCA2 (BRM). However, there are still insufficient data to suggest that such cases have a worse survival prognosis. In conclusion, the overall prognosis of SDSC patients is poor, and there is currently no standard treatment plan. Morphological examination combined with SMARCB1 (INI-1) immunohistochemical testing is the key to definitive diagnosis, and combined detection of SWI/SNF complex member proteins helps identify co-loss cases. Although co-loss cases are rare and the significance of their survival prognosis analysis is unclear, more clinical experience is needed.