Evaluation of Ki-67 Expression in Disordered Proliferative Endometrium, Endometrial Hyperplasia, and Endometrial Carcinoma

Introduction: Endometrial hyperplasia (EH) is characterized by elevated estrogen levels, which can lead to increased endometrial proliferation. Unopposed hyperestrogenism and elevated estrogen levels in conditions such as Lynch syndrome and estrogen-producing ovarian tumors can trigger endometrial proliferation and act as a predisposing factor for atypical endometrial hyperplasia (AEH) and endometrial carcinoma (EC). Recently, it has been considered that there is a progression from EH to endometrioid carcinoma. Disordered proliferative endometrium (DPE) is quantitatively similar to EH without atypia. The immunohistochemistry (IHC) marker Ki-67 reflects the degree of proliferation of malignant cells, as well as tumor invasion, metastasis, and prognosis in various malignancies. The aim of the study was to evaluate the expression of Ki-67 in DPE, EH without atypia, AEH, and EC, and to compare Ki-67 expression in low-grade and high-grade EC. Methodology: A hospital-based cross-sectional study was conducted in the Histopathology Section of the Department of Pathology using endometrial tissue samples obtained by endometrial curettage and hysterectomy from patients diagnosed with DPE, hyperplastic endometrium, and EC. For each case, an IHC study for the Ki-67 marker was performed. Results: Out of 68 cases of endometrial lesions, 21 (30.88%) were DPE, 13 (19.12%) were EH with atypia, 16 (23.53%) were EH without atypia, and 18 (26.47%) were EC. The mean total Ki-67 positivity in EC was 60.16±24.26; in AEH, 22.56±4.98; in EH without atypia, 7.86±6.21; and in DPE, 13.23±15.68. Conclusion: Ki-67 can help differentiate DPE from EH without atypia and AEH when diagnostic difficulty arises on Hematoxylin and Eosin (H&E)-stained slides. Ki-67 expression was significantly higher in high-grade ECs than in low-grade ECs, suggesting a role for Ki-67 as a prognostic indicator and biomarker of aggressiveness. Hence, Ki-67 marker studies should be routinely performed in endometrial lesions such as DPE, EH without atypia, and AEH.