Using this technique, we have studied a series of 212 early (pT1) unifocal breast cancers and have correlated the expression of uPA–PAI-1 complexes, together with other clinical and biological features (histologic variety, histologic and nuclear grade, hormone receptors, Ki67 labelling index, c-erb-B2-, p53- and CD44std-expression) with or without the occurrence of axillary node invasion. Here, NR4A1 is linked to breast cancer.