BackgroundCytochrome P450 2C19 (CYP2C19) enzyme is implicated in the metabolism pathway of many exogenous and endogenous substrates, including estrogens. The expression and activity of CYP2C19 are influenced by its genetic variability. Therefore, functional polymorphisms of CYP2C19 gene are expected to affect the catabolism of estrogens and consequently are associated with susceptibility to develop breast cancer. AimsUsing a case-control study, we investigated CYP2C19 polymorphisms: CYP2C19*2(rs4244285), CYP2C19*3(rs4986893) and CYP2C19*17(rs12248560) in Moroccan Breast Cancer patients compared to healthy women controls. We also tested association of these polymorphisms with several characteristics of these patients. MethodsCYP2C19 polymorphisms were genotyped in 440 subjects, including 220 histologically confirmed Breast Cancer patients and 220 healthy women controls. For each polymorphism, association between genotypes and Breast Cancer risk was evaluated as odds ratios with 95% confidence intervals adjusted for age and menopausal status. Furthermore, association of each CYP2C19 polymorphisms with tumor characteristics of Breast Cancer cases was investigated. ResultsNone of the CYP2C19 variants was significantly associated with Breast Cancer risk. However, carriers of CYP2C19*3 allele A showed an association with Triple-Negative Breast Cancer subtypes (P=0.02). ConclusionOur results highlighted a possible implication of CYP2C19*3 polymorphism and triple negative Breast Cancer through an unidentified mechanism. Further studies with more triple negative samples are needed to support this finding.