Mammography, and in special cases MRT, allow the detection of DCIS and microcarcinomas. Breast preserving surgery needs intraoperative care for tumor free margins. Decision making under favourable and unfavourable conditions is discussed. Tumor grading is important with respect to locoregional recurrences. Improvements in breast cancer diagnosis are discussed in a separate paper in the same volume. The significance of c-erbB2 in pT1N0M0 stage has been determined in 472 cases. Within the c-erbB family, c-erbB2 has highest significance. p53 should also be evaluated with respect to tumor progress. In a few cases of malignant cystosarcoma phyllodes, p53 reaction was found in epithelial and mesenchymal cell systems. These results correspond to the results of Domagala et al (90) which show that vimentin positivity correlates with high proliferation, a high degree of malignancy and c-erbB2 positivity. Finally, the significance of angiogenesis with respect to the ineffective knot-formation for tumor cell transport and detachment of epithelia with apoptosis are discussed. The significance of proteolytic activity of cancer according to the results of Schmitt et al (89) is included in the discussion. Biochemical analysis seems to be much more effective for prediction of metastatic process as compared with immunohistochemical evaluations.