In a case-control study nested within the Multiethnic Cohort (MEC), postmenopausal women with at least one C allele in the CYP1A2*1F gene had a lower risk of breast cancer than women with the common alleles [18], but a case-control study in Shanghai with women aged 25–64 years did not observe this association [19]. This evidence concerns the gene CYP1A2 and breast carcinoma.