Objective To investigate the clinicopathological features, immunophenotype, diagnosis and treatment of SMARCA4 (BRG1)-deficient carcinoma.

Methods Clinical data of 11 patients with SMARCA4 (BRG1)-deficient cancer were collected. The morphologic and immunohistochemical features of this tumour were summarized, and the relevant literature was reviewed.

Results Among the 11 cases of SMARCA4 (BRG1)-deficient carcinoma, eight were male and three were female, with median age of 60. Seven patients underwent radical resection, and four underwent traditional joint targeted chemotherapy and immunotherapy. Microscopically, the tumor cells were epithelioid, rhabdoid or spindle-shaped, with prominent eosinophilic nucleoli and frequent mitoses (>5/10 HPF). Multiple foci of necrosis were found in the tumor tissue, a large number of tumor emboli in the blood vessels and myxoid stromal degeneration. Among these cases, 11 cases showed loss of SMARCA4 (BRG1) expression, whereas the CK and Vim markers were expressed, SMARCB1 (INI1) expression was retained, and p53 mutation was detected. The tumor cells showed high proliferation activity (Ki-67>60%), and synaptophsin was moderately positive. Three cases were mismatch repair deficient and respectively showed the loss of MLH1/PMS2, PMS2 and MSH6 expression.

Conclusion The incidence of SMARCA4 (BRG1) -dificient carcinoma is low. It can be easily confused with other tumors and is difficult to be diagnosed before operation, which requires confirmation by immunohistochemistry.