Gastric SMARCA4-deificient undifferentiated carcinoma:A clinicopathological analysis of five cases

WANG Ruihan; SHI Dongxue; LV Beibei; LIN Xiaoyan

doi:10.3969/j.issn.1007-8096.2025.11.1438

Abstract：Objective To investigate the clinicopathologic features and immunohistochemical characteristics of gastric SMARCA4-deficient undifferentiated carcinoma,in order to improve the understanding of the disease and to avoid underdiagnosis and misdiagnosis.Methods Five cases of gastric SMARCA4-deficient undifferentiated carcinoma diagnosed in the Department of Pathology,Provincial Hospital of Shandong First Medical University from September 2022 to February 2025 were collected,and their clinical data,pathological features,immunohistochemical staining results and follow-up were analyzed and summarized.Results The five patients were all elderly men,with the age of onset ranging from 59 to 73 years,and the median age was 68 years.The clinical symptoms were mainly abdominal discomfort,some of which were accompanied by abdominal distension,belching or abdominal pain.Pathological examination showed that the tumors occurred in different parts of the stomach,and were generally protruded or ulcerative masses with a maximum diameter of 4～6 cm,and the tumor cells were of various morphologies and obvious heterogeneity under the microscope,and some of them showed transverse muscle-like changes.Immunostaining staining results exhibited loss of BRG-1 expression,INI-1 was diffusely positive,mismatch repair proteins were positive(pMMR);neuroendocrine marker synaptophysin demonstrated focally weak positivity and CgA was negative;the Ki-67 proliferation index was 70%～90%;P53 staining results were diverse;HER2 staining was 0-1+in 3 cases,and 2+in 2 cases.In situ hybridization for EBER was all negative.2 patients underwent postoperative chemotherapy or a combination of chemotherapy plus immunotherapy and were followed up for 1-28 months,and all cases were still alive.Conclusion Gastric SMARCA4-deficient undifferentiated carcinoma is rare,with diverse histomorphological patterns,and the diagnosis needs to be combined with immunohistochemistry.Clinicians should improve their knowledge of this disease to avoid misdiagnosis and missed diagnosis.