To study PRL-3 expression in preinvasive and invasive breast cancer, in this study tissue samples from 135 patients with ductal carcinoma in situ (DCIS) and 147 patients with invasive breast cancer, diagnosed between 1993 and 1997 at the Department of Gynaecology, University Münster, Germany, were analysed. Here, PTP4A3 is linked to invasive breast carcinoma.