Introduction: Breast cancer is a complex aggressive disease with different subtypes due to multiple biomolecular interactions (genetic heterogeneity) and demonstrates the extensive variation in patients clinical feature based on the ethnic group that makes the diagnosis and treatment challenging. Numerous breast cancer markers had been established like Progesterone Receptor (PR), Estrogen Receptors (ER), Human Epidermal growth factor Receptor (HER2neu) as well as clinical-pathological factors such as the stage of the disease, extent of axillary lymph node involvement, tumour size, histological grade, a mitotic rate, patient age, menopausal status etc. Ki?67, cyclin D1, cyclin E, and ER__ampersandsignbeta; had been advocated to exhibit both the predictive and prognostic value in breast cancer patients. Objectives: The objective of the current study is to evaluate the relevance and correlation of Ki-67 index in relation with other clinicopathological factors that determine the prognosis in Carcinoma breast and thereby, defining the staining thresholds and cut-off of Ki-67 immunohistochemistry. Methods: A consecutive number of 200 patients who had undergone modified radical mastectomy were included in this study. The postoperative specimen was for the assessment of histopathology diagnosis and the tumour size, nodal status, histological grading, tumour pathological type, mitotic rate, and lymphovascular invasion apart from Estrogen Receptor status, Progesterone Receptor status, Human Epidermal growth factor Receptor 2neu status and Ki-67 protein expression. Patient__ampersandsignrsquo;s clinical data were collected prospectively. SPSS software version 19 was used for statistical analysis. One way Anova and chi-square analysis was applied to assess the relation of Ki-67 index score with other prognostic factors. Results: Ki-67 protein expression showed no correlation with age (irrespective of age classification), menopausal status, histological subtypes, lymphovascular invasion, mitotic rate, ER and HER2neu, but still the levels of Ki-67 protein increases with ER negativity (p__ampersandsigngt;0.05). The overall histological grading showed statistical significance between grade I Vs III and grade II Vs III which reflects the linear relationship whereas chi-square analysis did not show. Progesterone Receptor showed an inverse relationship with Ki-67 expression (p=0.0005) and whereas, tumour size and nodal involvement revealed a linear relationship(p=0.02). Conclusion: Hence, the study had lucidly established the fact that Ki-67 index is superior to the mitotic rate and can be routinely employed for predicting the prognosis in breast cancer patients. The current paper recommends the use of the staining thresholds and cut-offs of Ki-67 immunohistochemistry used in the current study for future studies since all the patients expressed Ki-67 protein.