Immunohistochemical Evaluation of PD-L1 Expression in Complex Atypical Hyperplasia and Early-Stage Endometrial Cancer

INTRODUCTION: The study aims to evaluate programmed cell death ligand-1 (PD-L1) expression in complex atypical hyperplasia and early-stage endometrial cancer and to assess its association with tumor grade. MATERIALS AND METHODS: This retrospective study was conducted at a single tertiary university hospital and included hysterectomy specimens obtained between 2010 and 2020. A total of 80 cases were analyzed: 20 with complex atypical hyperplasia and 60 with Stage IA endometrioid endometrial cancer, comprising 20 Grade 1, 20 Grade 2, and 20 Grade 3 tumors. All specimens underwent immunohistochemical staining with the PD-L1 (22C3) antibody, and PD-L1 expression was assessed using the combined positive score. RESULTS: PD-L1 expression was absent in complex atypical hyperplasia but present in 4 of 20 Grade 1 cases (20%), 6 of 20 Grade 2 cases (30%), and 16 of 20 Grade 3 cases (80%). PD-L1 positivity increased significantly with higher tumor grade (p < 0.001). No significant associations were identified between PD-L1 expression and patient age, tumor diameter, depth of myometrial invasion, endometrial confinement, or lymphovascular invasion. DISCUSSION: PD-L1 expression appears to be detectable in early-stage endometrioid endometrial cancer and may increase with tumor grade, suggesting early immune checkpoint activity. CONCLUSION: PD-L1 expression may be associated with tumor grade in early-stage endometrioid endometrial cancer. However, its clinical significance remains unclear. These findings may be relevant in the context of fertility- preserving management and require further investigation.