CYP19A1 and breast cancer: Current endocrine therapies for breast cancer are mainly based on targeting the ERα signalling pathway: reducing oestrogen abundance with aromatase inhibitor (Baum et al, 2002; Johnston & Dowsett, 2003), antagonizing ERα function with tamoxifen and raloxifene (Jensen & Jordan, 2003) or down-regulating ERα expression with fulvestrant (MacGregor & Jordan, 1998).