Role of immunocytochemistry in diagnosis of prostatic neoplasia by fine needle aspiration biopsy

The efficacy of immunocytochemical staining for prostate specific antigen (PSA) and prostate‐specific acid phosphatase (PSAP) was studied in aspiration biopsy specimens from 19 patients. Eighteen patients had prostatic carcinoma and one had hyperplasia of prostate. Specimens were obtained from both the primary tumors and metastatic sites. Immunoperoxidase staining was performed on alcohol‐fixed cytology smears (some prepared up to 9 years previously) using appropriate antisera followed by an avidin‐biotinylated horseradish peroxidase complex. Results were scored according to the percentage and intensity of positively stained malignant cells. Corresponding histologic specimens were stained and scored in a similar fashion. Correlations were made between the staining characteristics of the tumor markers and grade of tumor, using the University of Texas M. D. Anderson Hospital classification of prostate carcinoma. Overall there was good correlation between cytologic and histologic specimens for the presence of PSA and PSAP, although metastases tended to show fewer positively stained cells than the primary tumor. There was no relationship between tumor grade and percentage of positively stained cells. Ninety‐three percent of aspirated primary and secondary prostatic tumors stained positively for PSAP compared with 81 % for PSA. In one of 3 patients, negative staining of neoplastic cells by both PSAP and PSA was helpful in confirming the existence of a second primary tumor.