TFF1 and breast cancer: TFF1 expression is associated with increased incidence of breast cancer metastasis to bone (Smid et al., 2006), high levels of TFF1 expression in metastatic tumour cells renders it a reliable marker of micrometastases (Mikhitarian et al., 2005) and expression is increased in tumours that arise during the interval between routine breast cancer screening (Crosier et al., 2001).