The aim of this study was i) to determine the intratumoral heterogeneity of 35 proteins representing the HER2, EGFR, and uPA/PAI-1 signaling pathways in large (≥3 cm) primary breast carcinomas, and ii) to identify differences in protein expression levels between axillary lymph node metastases from the same patient. Here, SERPINE1 is linked to breast carcinoma.