In our previous study, the CYP2C19 deletion allele was found twice as frequent in familial breast cancer cases (5.8%) as in controls (2.3%), whereas CDH19 was observed once in both familial (1.0%) and control cohorts (0.8%) [4], implicating the need for a larger dataset for the evaluation of their disease relatedness. Here, CYP2C19 is linked to breast cancer.