[Gastric SWI/SNF-complex deficient undifferentiated/rhabdoid carcinoma: a clinicopathological study].

Objective: To investigate the clinicopathological features, immunohistochemical characteristics, differential diagnosis and prognosis of gastric SWI/SNF-complex deficient undifferentiated/rhabdoid carcinomas. Methods: Two cases of gastric SWI/SNF-complex deficient undifferentiated/rhabdoid carcinoma were collected at Fudan University Shanghai Cancer Center, Shanghai, China from 2017 to 2018. The clinicopathological characteristics were analyzed. Hematoxylin and eosin, and immunohistochemical stains were performed, and the relevant literatures were reviewed. Results: The two patients were both male, aged 60 and 74 years, respectively. Their symptoms were both abdominal pain. The tumor arose in the esophagogastric junction in case 1, and the cardia to the fundus and the posterior wall of the upper part of gastric body in case 2. Both tumors were present as an ulcerative mass. The patients died of tumor 11 months and 8 months after surgery, respectively. Histologically, the tumor cells arranged in sheets, nests, cords or trabecular patterns, and pseudoavleolar structure. The tumor cells were epithelioid with uniform morphology, while the tumors showed scant stroma and massive necrosis. Variable rhabdoid cells and multinucleated giant cells were seen in both cases. SMARCA4 encoding protein BRG1 was undetectable in both tumors, while SMARCB1 encoding protein INI1 was detected. The tumor cells were diffusely positive for vimentin and negative for epithelial marker (CKpan), gastrointestinal stromal tumor markers (CD117 and DOG1), myogenic markers (desmin and myogenin), melanoma markers (S-100 protein, SOX10 and HMB45), and lymphohematopoietic markers (LCA and CD20). Conclusions: Gastric SWI/SNF-complex deficient undifferentiated/rhabdoid carcinoma is a rare and highly aggressive tumor with poor prognosis. The detection of subunits protein expression of SWI/SNF complex is important for diagnosis of the tumor.