Pathology

Abstract

Background: High grade prostatic intraepithelial neoplasia (HGPIN) is the only established precursor for prostate cancer (PCa), with high predictive value as a marker for PCa. About 2% of contemporary needle biopsies contain collections of small acini suspicious for PCa but which fall below the diagnostic threshold. These cases are reported as atypical small acinar proliferation suspicious for but not diagnostic of malignancy (ASAP). Identification of HGPIN, ASAP, or both, warrant repeat biopsy for concurrent or subsequent PCa. PCa has been reported occur in up to 36% of subsequent biopsies for HGPIN and up to 60% for ASAP. We report results of follow up biopsies in a patient population with long term close clinical follow up, a population in which earlier, less advanced lesions are detected. Design: All patients were from community practices, and had serum prostatic specific antigen studies obtained annually or more frequently. 191 cases with an initial diagnosis of 1) HGPIN 2) ASAP or 3) both HGPIN and ASAP; and at least 1 set of subsequent biopsies were retrieved from the files of Bostwick Laboratories. Cases with concomitant PCa were excluded. Follow up biopsies for each entity were separated into 2 diagnostic categories 1) Ca or 2) Non-PCa. Results: Repeat biopsies were obtained from 1 week to 14 months after the initial diagnosis. Results are as follows: HGPIN PCa, 23/103 (22%); HGPIN Non-PCa, 80/103 (78%); ASAP PCa, 18/49 (37%); ASAP Non-PCa, 31/49 (63%); HGPIN & ASAP PCa 11/39 (28%); and HGPIN & ASAP Non-PCa 28/39 (72%). Conclusions: The predictive accuracy for PCa is lower for both HGPIN and for ASAP in a highly screened patient population compared with previously reported unscreened populations. It is still significant compared with historic controls with neither HGPIN nor ASAP. The combination diagnosis of HGPIN & ASAP is an intermediate predictor for PCa, weaker than for ASAP, but stronger than for HGPIN. Other factors that may account for the decline in the predictive accuracies of HGPIN and ASAP for PCa seen here include: 1) more extensive prostate sampling 2) a greater number of biopsies obtained 3) addition of more lateral biopsies.