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

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).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.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.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.