CYP19A1 and breast cancer: Primary breast cancer survival rates have improved dramatically over the last three decades, both in relationship to itself and relative to other cancers.1 This improvement has been achieved, at least partially, through the increased effectiveness of targeted endocrine therapies such as aromatase inhibition2 and modulation of oestrogen receptor signalling, as well as the development of monoclonal antibodies targeting the HER2/neu receptor.3 Despite these manifest improvements in prognosis there are still some areas in breast cancer treatment that remain challenging.