The variant CYP2C19*3 (rs57081121) which lead to a decreased activity of the CYP2C19 has been associated with increased risk in Asians (Gan et al., 2011) and the variant CYP2C19*17 (rs12248560) causing an ultra rapid metabolizer phenotype leads to a decreased HRT-related breast cancer risk in Europeans (Justenhoven et al., 2012). This evidence concerns the gene CYP2C19 and breast carcinoma.