Objective: This study aimed to evaluate the association between pre-operative progesterone receptor (PR) and p53 expression and prognosis in pre-operative grade 2 endometrioid endometrial carcinoma compared with grade 1 and grade 3 carcinomas.

Methods: Three European endometrial carcinoma cohort studies were included. Patients with pre-operative grade 2 endometrioid carcinoma and known pre-operative PR and p53 status were included (n = 400), as were patients with pre-operative grade 1 (n = 602) or grade 3 (n = 148) endometrioid carcinomas. Kaplan-Meier and Cox regression analyses were performed to analyze disease-specific and disease-free survival.

Results: Patients with pre-operative grade 2 endometrial carcinoma and wild-type p53 plus PR-positive expression showed a similar 7-year disease-specific survival to grade 1 endometrial carcinoma patients (95.8% vs 97.5%, p = .13), while the 7-year disease-specific survival of patients with grade 2 endometrial carcinoma with p53 aberrant and/or negative PR expression (83.5%) was significantly lower (p < .001). The combination of these markers was an independent prognostic factor in multivariate Cox regression analyses.

Conclusions: The prognostic impact of pre-operative p53 and PR expression in patients with grade 2 endometrioid endometrial carcinoma supports a modified binary grading system in which grade 2 patients should be pre-operatively classified as low- or high-grade depending on p53 and PR expression.