The prognostic significance of Ki 67/MIB1 immunohistochemical assays (ICAs) was investigated in optimal technical conditions in 139 breast carcinomas. Automated ICAs (immunoperoxidase/Ventana device) was performed on frozen sections. Immunoprecipitates were quantified by computerized analysis (SAMBA) of digitized microscopic images. Mean positive surfaces (%) and quantitative immunocytochemical (QIC) index were correlated to the patients survival (8-year survival). The results showed that Ki 67/MIB1 large surfaces (cutpoint, 20%) and high QIC index (cutpoint, 12) correlated with poor overall survival (Kaplan Meier, log rank test, p=0.011 and p=0.037, BMDP software). In node positive, but not in node negative patients, large Ki 67/MIB1 surface (cutpoint, 20%) and high QIC index (cut-off 12) correlated with the overall patient survival (p=0.0037 and p=0.049). Also large Ki 67/MIB1 positive surface (cut-off, 20%) correlated with disease-free survival in all patients and node positive patients (p=0.022 and p=0.0057) but not in node negative patients. It is concluded that in optimal technical conditions (automated and quantitative immunohistochemical assays on frozen sections) Ki 67 antigen immunohistochemical expression in breast carcinomas tissue has a prognostic significance in node positive patients but not in node negative patients.

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