ASSESSMENT OF TUMOUR PROLIFERATION BY USE OF THE MITOTIC ACTIVITY INDEX, Ki67, AND PHOSPHOHISTONE H3 EXPRESSION IN INFILTRATING DUCTAL CARCINOMA OF BREAST

Introduction: Inltrating ductal carcinoma (IDC) of the breast is the most common subtype of breast cancer, necessitating precise prognostic markers. Phosphohistone H3 (PHH3) is a novel marker of mitotic activity that may offer superior prognostic information compared to traditional markers like Ki67 and the mitotic activity index (MAI). Despite the widespread use of proliferation markers like Ki67 and the Mitotic Activity Index (MAI) in breast cancer prognosis, their low reproducibility and subjective interpretation limit their usefullness. Phosphohistone H3 (PHH3) has shown promise as a more reliable marker due to its specicity for mitotic cells, yet its relationship with traditional markers like Ki67 in breast cancer remains underexplored. This study is needed to clarify the potential of PHH3 in improving prognostic accuracy, particularly in inltrating ductal carcinoma, and to establish its role in enhancing breast cancer grading and guiding personalized treatment decisions. Aims: To assess PHH3 and Ki67 expression in inltrating ductal carcinoma of the breast and correlate it with mitotic activity index. Additionally, to investigate their association with histological grade and TNM stage of the carcinoma. Objectives: The study aims to evaluate PHH3 expression in IDC and compare its effectiveness with Ki67 and MAI in correlating with histological grade and tumor staging. Specically, it seeks to: 1. To assess PHH3 expression levels in IDC. 2. To correlate PHH3, Ki67, and MAI with histological grade and TNM stage of IDC. Results: PHH3 expression was observed in 40.3% of cases and showed a stronger correlation with MAI compared to Ki67. High PHH3 expression was more consistently associated with higher histological grades and advanced tumor stages, demonstrating its superior prognostic value over Ki67 and MAI. Conclusions: PHH3 is a superior biomarker for assessing proliferation in IDC compared to Ki67 and MAI. Its stronger correlation with histological grade and tumor staging underscores its potential to enhance prognostic accuracy and guide treatment decisions, leading to improved patient outcomes.