[Dedifferentiated endometrial carcinoma/undifferentiated endometrial carcinoma with loss of expression of SMARCA4: clinicopathological features analysis].

Objective: To investigate the clinicopathological characteristics of dedifferentiated endometrial carcinoma/undifferentiated endometrial carcinoma (DDEC/UDEC) with loss of expression of SMARCA4. Methods: A total of 10 cases with loss of expression of SMARCA4 were diagnosed at Fujian Cancer Hospital between January 2019 and December 2023. A retrospective analysis was conducted on the clinical characteristics, morphology, immunophenotype, molecular classification, and prognosis. Results: (1) Clinical characteristics: among 10 cases of DDEC/UDEC with loss of expression of SMARCA4, the patients' age ranged from 48 to 65 years, with a median age of 56 years.Five cases were classified as International Federation of Gynecology and Obstetrics (FIGO) stages Ⅰ-Ⅱ, while the remaining five were categorized as stages Ⅲ-Ⅳ. (2) Pathological features: tumor cells exhibited poor cell adhesion, with common intravascular tumor emboli (8/10), occasional vacuolated nuclei (6/10), rhabdoid cells (4/10), and starry sky phenomenon formed by tissue cell phagocytosis apoptosis bodies or fragments (4/10). Six cases (6/10) showed loss of mismatch repair (MMR) protein expression, two cases (2/10) exhibited p53 mutant expression, and five cases (5/10) tested positive for programmed cell death ligand 1 (PD-L1). (3) Molecular subtyping: molecular subtyping revealed POLEmut in 1 case (1/10), mismatch repair deficient (MMR-d) in 5 cases (5/10), p53 abn in 1 case (1/10), and no specific molecular profile (NSMP) in 3 cases (3/10). (4) Prognosis: the follow-up period ranged from 7 to 42 months, with a median of 20 months. Five patients succumbed to the tumor, whereas the remaining five exhibited no recurrence during subsequent postoperative evaluations. The 2-year progression-free survival rates and overall survival rates were 58.3% and 52.5%, respectively. Conclusions: Loss of expression of SMARCA4 occurs in approximately 1/5 of DDEC/UDEC, which presents with an aggressive clinical course and a poor prognosis. About half of them show MMR protein loss expression and PD-L1 positive expression, suggesting that there might be benefit from treatment with immune checkpoint inhibitors.