Purpose of Investigation: This study aims to investigate PIBF expression levels in normal, hyperplastic, and endometrioid adenocarcinoma paraffin blocks. The purpose of this study is to determine the PIBF expression levels in endometrial cancer cells. Materials and Methods: A total of 90 patients were investigated. Thirty of those were diagnosed as having normal endometrial tissue, 30 had endometrial hyperplasia, and 30 had endometrioid adenocarcinoma. The expression of PIBF was assessed using immunohistochemically using paraffin-embedded tissue blocks. Results: Tissue sections were compared based on immunostaining with PIBF. The authors detected higher stromal PIBF expression in the endometrioid adenocarcinoma group as compared to the endometrial hyperplasia and normal endometrium groups (p < 0.001). The glandular PIBF expression did not differ among the groups (p > 0.05). Conclusions: Endometrial cancer cells have higher levels of expression of PIBF protein than normal endometrial tissue and endometrial hyperplasia tissue based on immunohistochemistry staining. PIBF immunostaining may be helpful in preoperatively differentiating between atypical endometrial hyperplasia (AEH) and endometrioid adenocarcinoma (EC) in suspicious cases.