In summary, centered on the AURKA-HMMR-TPX2-TUBG1 functional module that regulates mammary epithelial polarization, this study confirms previous association results for HMMR rs299290 and suggests novel associations (for AURKA/CSTF1 and HMMR-rs299290 interactions) with breast cancer risk in BRCA1 and/or BRCA2 mutation carriers. Here, BRCA2 is linked to breast cancer.