Immunoperoxidase demonstration of prostatic acid phosphatase in aspiration biopsy cytology (ABC)

The authors investigated the usefulness of immunoperoxidase demonstration of prostate-specific acid phosphatase (PAP) in determining the tissue of origin for carcinoma in aspiration biopsy cytology (ABC) specimens. Antisera from a commercial kit were applied using standard technics directly to Papanicoloau-stained slides. PAP was diffusely positive in numerous tumor cells of 27/28 moderately or poorly differentiated and 17/18 well-differentiated primary prostatic carcinomas. A negative result upon substituting the primary antiserum confirmed the reaction specificity in 18 cases with an additional available slide. PAP was demonstrable in corresponding histologic sections of 16/17 moderately or poorly differentiated and 18/18 well-differentiated carcinomas. Only 2 of 22 nonprostatic carcinomas (both of breast origin) showed very rare positive cells. Four ABC specimens of metastatic prostatic carcinoma were diffusely positive. Thus, diffuse staining of PAP by immunoperoxidase in tumor cells of ABC specimens gives high sensitivity and specificity for prostate as the tissue of origin.