Distinct histological and clinical features associated with pure uterine serous carcinoma: A single institution experience

Aim: To ascertain the clinicopathological features, survival, and prognostic factors of pure uterine serous carcinoma (pUSC) and compare its clinicopathological characteristics with those of serous-like grade-3 endometrioid endometrial carcinoma (G3-EEC).Method: Consecutive patients with pUSC and p53 abnormal (p53abn) G3-EEC were retrospectively selected between 2014 and 2022. Histological and immunohistochemical features were reviewed, clinical information was collected, and survival analyses were performed.Results: Eighty-five pUSC patients (mean age: 61.6 years) were included. Histologically, pUSC showed a predominantly glandular growth pattern (80.0 %) with high-grade nuclear atypia and obvious nucleoli and 53 cases showed admixtures of architectural patterns. The p53 aberrant expression rate was 98.8 %. 41.5 %, 53.7 %, and 67.5 % of cases were classified as negative for ER, PR, and WT1, respectively. Six (12.3 %) of 49 cases had a HER2 score of 3+ by immunohistochemistry (IHC). The overall survival and progression-free survival rates were 72.9 % and 63.5 %, respectively. Advanced stage, no adjuvant therapy, and lymph node metastasis were independent risk factors for poor survival in pUSC. Twenty-five p53abn G3-EEC patients were assessed. Women with p53abn G3-EEC were on average, younger than those with pUSC (53.4 vs. 61.6 years, P < 0.001). Papillary structures were observed more commonly in pUSC (16 % vs. 36.5 %, P = 0.042). Positive PR expression was significantly associated with p53abn G3-EEC (P = 0.009). Survival did not differ significantly between the subgroups in univariate and multivariate analyses.Conclusion: In this contemporary series, we affirm the suboptimal prognosis associated with pUSC, and that the survival associated with pUSC and p53abn G3-EEC are not significantly different. pUSC and p53abn G3-EEC have distinct morphological and immunohistochemical characteristics.