SERPINE1 and breast cancer: In conclusion, the detection of uPA–PAI-1 complexes inside the tumour cells in early (T1) breast cancers expressing progesterone receptors is associated with a significantly higher incidence of axillary metastasis, and this might be of clinical value at the present time, where there exists an increasing trend towards avoiding axillary dissection at all in the presence of very small breast cancers with clinically negative axillae.