CYP19A1 and breast cancer: On the other hand, examination of two single nucleotide polymorphisms in Cyp 19 gene (aromatase), rs1008805 (A/G) and rs730154 (C/T) revealed that premenopausal women carrying at least one G alelle at Cyp 19 locus was associated with an increased breast cancer risk (Talbot et al., 2008).