An immunoperoxidase technique to aid in the differential diagnosis of prostatic carcinoma

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The differentiation of carcinomas arising in the prostate, bladder, and rectum may be a diagnostic problem when a neoplasm demonstrates extensive local invasion of adjacent organs. With the advent of enzyme-labeled antibody techniques, the specific identification of these neoplasms is potentially within the grasp of the pathologist.1, 2 However, the value of these techniques is limited by the specificity of available antibodies. Cross-reactivity, if not detected before clinical application, could result in diagnostic error.

We describe an immunoperoxidase method3 to demonstrate the presence of prostatic acid phosphatase in neoplasms of prostatic origin, with the use of an antibody raised in rabbits against this enzyme. The potential application of this technique to differential diagnosis is discussed and the importance of in-house testing of these antibodies is demonstrated.

Materials and methods

The following immunochemicals were used in this study to examine paraffin-embedded tissue fixed in zinc-substituted Zenker’s solution: (1) rabbit anti-human prostatic acid phosphatase, (2) sheep anti-rabbit immunoglobulin, and (3) peroxidase-rabbit antiperoxidase complex (PAP). All antibodies were obtained from Immulok.

Tissue from 54 cases was examined. Four-micron sections of tissue, two per slide, were cut and dried on albuminized slides at 60 C overnight. The sections were deparaffinized in xylene and graded alcohols and washed in phosphate-buffered saline (PBS), pH 7.2 (FTA hemagglutination buffer, BBL) until miscible. Endogenous peroxidase activity was consumed by a 3-minute incubation in 3% hydrogen peroxide followed by a PBS wash. Sections were then incubated with normal sheep serum for 20 minutes to block nonspecific binding of the . . .



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