Prostatic intraepithelial neoplasia in prostate specimens: frequency, significance and relationship to the sampling of the specimen (a retrospective study of 121 cases).

Objectives: To determine the frequency of PIN (prostatic intraepithelial neoplasia) in prostate specimens and the relationship of PIN with PCA (prostatic carcinoma) and amount of sampling of the specimen.

Materials And Methods: All the haematoxylin-eosin stained slides of 121 cases diagnosed between 1990 and 1995 were re-examined retrospectively. The amount of sampling of prostate specimens was also re-examined.

Results: PIN was observed in 47.9% of all prostate specimens. The frequency of incidental PIN was 71.4% in cystoprostatectomy specimens. PIN was present in 58.3% of the cases with PCA. We observed foci of high-grade PIN adjacent to sites of invasive carcinoma in 100.0% of prostatectomy specimens with PCA. PIN was high-grade in 100.0% of the carcinomatous prostates with PIN. It was multifocal in 53.4% of 58 cases with PIN. Incidental PCA was identified in 14.3% of cytoprostatectomies for bladder cancer. The average number of paraffin blocks of prostatic tissue was 4.1 (+/-2.6) in cases with PIN and 3.2 (+/-1.4) in cases without PIN.

Conclusion: In prostate specimens, the determination of PIN is very important since it is the most likely precursor of PCA. The probability of detecting PIN and PCA in a prostate specimen is directly related to the amount of sampling.