[SMARCA4-deficient uterine sarcoma: a clinicopathological analysis of five cases].

Objective: To investigate the clinicopathological features of SMARCA4-deficient uterine sarcoma. Methods: Five cases of SMARCA4-deficient uterine sarcoma at the Department of Pathology, the First Affiliated Hospital of Nanjing Medical University from 2018 to 2024 were collected. The morphological and immunohistochemical features were observed and analyzed. A follow-up study was also carried out. Results: Five female patients, aged 24, 54, 56, 61, and 41 years, respectively, presented with vaginal bleeding or abdominal pain. All patients had imaging findings of intracavitary lesion in the uterus, with tumor sizes ranging from 3.0 cm to 8.8 cm. The patients were followed up for 2 to 14 months. Case 1 died 9 months after surgery, whereas the remaining four patients were still alive. Histologically, the tumor cells exhibited a diffuse growth pattern, with an infiltration depth involving more than half of the myometrium. Portions of the interstitium appeared sclerosed. Benign endometrial glandular structures were observed in a leaf-like or fissured pattern, resembling those of uterine adenosarcoma. The tumor cells were large epithelioid with abundant or faintly eosinophilic cytoplasm, and the nuclei were moderately to markedly atypia with prominent nucleoli and brisk mitosis. Rhabdoid cells were seen. Some areas showed small round blue cells, with occasional spindle cells and myxoid stroma. Additionally, widespread or focal lymphovascular space invasion was observed within the myometrium. All five cases exhibited absence of SMARCA4 (BRG1) expression and retained SMARCB1 (INI1). Claudin4 expression was negative. There was no deficient expression of mismatch repair proteins MLH1, PMS2, MSH2 and MSH6. p53 showed wild-type expression. Ki-67 index ranged from 30% to 60%. CKpan, CK7, ER, PR, and PAX8 were negative. Conclusions: SMARCA4-deficient uterine sarcoma is rare, highly aggressive, and has a poor prognosis. The tumor exhibits a broad morphological spectrum, with rhabdoid cells and adenosarcoma-like structures serving as important diagnostic clues. The absence of BRG1 expression lends support to a definitive diagnosis.