BMI1 is the first functional mammalian Polycomb group (PcG) proto-oncogene involved in multiple biological processes. Regulation of B cell-specific Moloney murine leukaemia virus integration site 1 (BMI1) expression with increase in histological grades of breast carcinoma in correlation with hormone receptor status was studied in 60 Indian breast cancer patient's formalin-fixed paraffin-embedded tissue blocks. Relative expression of BMI1 was studied using real-time PCR. Immunohistochemistry explained the distribution of hormone receptor markers. Correlation of BMI1 gene expression with oestrogen receptor, progesterone receptor (PR) and human epidermal growth factor receptor 2/neu status was analysed using Hex-protein docking tool. The hormone receptor expression was reduced with increasing grades of breast tumour. BMI1 gene expression was downregulated (real-time polymerase chain reaction analysis). Docking analysis explained the correlation between BMI1 and PR expression. BMI1 gene was co-regulated (down) with PR in the invasive ductal breast carcinoma with relative progression explicating it a diagnostic biomarker for ductal carcinoma of the breast.