The important step of breast cancer genesis is the early change of functional activity of cytosolic enzymes (esterases) in peripheral blood mononuclear cells. Such transformations in PBMC may be detected accurately by an existing device Flowcytometer (FACS™ MultiSET™ System, company "Becton Dickinson" GmbH, USA), where measurements of fluorescence polarization and enzymatic hydrolysis of FDA substrate are recorded. A conclusion about presentation of breast cancer among examined women is achieved by "CDT" (cancer detection technology) software, which analyzes mathematically the results of fluorescence polarization and enzymatic hydrolysis.