In the context of breast cancer predisposition, our study suggests there is cross talk between the alleles of proteins of different cancer pathways including DNA repair and the immune system (XPD-[Lys751Gln] and IL10-[G(-1082)A]), cell cycle and estrogen metabolism (COMT-[Met108/158Val] and CCND1-[Pro241Pro]), cell cycle and DNA repair (BARD1-[Pro24Ser] and XPD-[Lys751Gln]) as well as within a single pathway such as estrogen metabolism (GSTP1-[Ile105Val] and COMT-[Met108/158Val]). This evidence concerns the gene COMT and breast carcinoma.