The absence of basal cell layer of prostatic acini containing high-molecular cytokeratin, which is immunohistochemically detected by monoclonal antibody 34betaE12, is an essential diagnostic characteristic of prostatic cancer. The absence of immunohistochemical reaction in 3 or more pseudoglandular structures of prostatic tissue indicates malignant process. The percentage of immunohistochemically completely negative glandular structures was determined by semiquantitative measurement in tissue specimens obtained by TRUS biopsy of the prostate, and it was correlated with serum PSA concentration and Gleason score. The increase of percentage of glandular prostatic formations completely negative to high-molecular cytokeratin detected by 34betaE12 led to simultaneous rise of mean value of Gleason prostatic cancer score (p < 0.001) as well as the average serum PSA concentration in subjects (p < 0.05).