Prostatic adenocarcinoma labelled with a monoclonal antibody and polyclonal serum: A quantitative assessment

Objective To investigate the detection of tissue prostate-specific antigen (PSA) using a monoclonal antibody or polyclonal serum in patients with localized prostate cancer. Patients and methods Fifteen samples of prostatic tissue from patients with localized prostate cancer were assessed for PSA using monoclonal antibodies and polyclonal serum. The intensity and area of chromogen precipitation in several microscopic fields was determined using image analysis. Results There were significant differences in the intensity and distribution of PSA labelling in the tumour between the methods; polyclonal serum was more sensitive in detecting PSA in tissue sections. Notably, there was a focal 'possible clonal' pattern of negative labelling with the monoclonal antibody, which contrasted with the positivity of the polyclonal marker. Conclusions The loss of PSA expression in some poorly differentiated cancers may represent the loss of specific epitopes rather than loss of the entire protein.