Background: Based on the TCGA endometrial cancer study results, a clinically applicable classification that identifies distinct subgroups with prognostic signature, the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE), has been built and validated. It shows that those with abnormal expression of p53 (p53abn) are the group with the worst prognosis. We attempted to explore the association of p53abn and progesterone receptor (PR) in endometrioid endometrial cancer. Methods: We included 397 consecutive endometrial cancer cases of endometrioid histology with adequate tumor tissue in the formalin-fixed, paraffin-embedded (FFPE) block and available follow-up information. This study was granted by Chang Gung Medical Foundation IRB 201702242B0D001. Sanger sequencing to assess the POLE exonuclease domain hotspot mutations of exon 9-14 and immunohistochemical staining on FFPE tumor tissue sections for p53, ER, PR, and mismatch repair proteins were performed. Immunohistochemical p53 expression of cancer cell nucleus was recorded as completely negative (0%), weakly positive (1-59%), and diffusely strong positive (>60%). Tumors with weak positive p53 staining were defined as p53 wild type (p53wt), while the other two were defined as p53 abnormal (p53abn). PR scores were calculated by multiplying the average staining intensity by the tumor cell nucleus stained percentage. We arbitrarily defined a progesterone receptor score of 100 or higher as positive (PR+). Progression-free and endometrial cancer-specific overall survivals starting at the date of diagnosis were evaluated using Kaplan-Meier method and compared by log-rank test between groups. Results: PR was positive in 82% of all studied cases. Of the 48 cases with p53abn tumor, 35(73%) were PR (+). With a median follow-up of 74 months, the progression-free survival and cancer-specific survival of patients with PR+ tumors (N = 310) were 93% and 96.8%, respectively, compared with 75% and 85.7% of those with PR- tumors (N = 70) (both p < 0.001, log-rank test). Among those with P53abn, PR expression was associated with a favorable progression-free survival (p = 0.081) and better cancer-specific survival (p = 0.044). POLEmut, POLE mutated; dMMR, deficient mismatch repair PR+, progesterone receptor score ≥100, ER+, estrogen receptor score ≥100; p53abn, abnormal p53 expression. MMR was undetermined in 32 cases, PR in 17 cases, ER in 17 cases, and p53 was undetermined in 10 cases. POLE status was detected in all cases. Cases with POLE wild type, proficient mismatch repair, progesterone score < 100, estrogen score < 100 and wild type p53 were not listed in this table. Conclusions: Our study showed that incorporating PR into prognostic molecular markers for endometrioid endometrial cancer might provide further risk stratification.