Clinical significance of high-grade prostatic intraepithelial neoplasia in transurethral resection specimens

High-grade prostatic intraepithelial neoplasia (PIN) is the most likely precursor of invasive prostatic adenocarcinoma. The incidence and clinical significance of this lesion have not been previously defined in specimens from transurethral resections of the prostate (TURP).

To determine the frequency of PIN in TURP specimens and its relationship with adenocarcinoma, we reviewed 698 resections performed at Mayo Clinic between 1989 and 1990. A mean of 6 slides was analyzed for each case (range 1 to 36). The presence, extent, and architectural pattern of PIN were recorded. The results were correlated with many clinical and pathologic features, including patient age, Gleason score, stage, serum prostate-specific antigen (PSA) concentration, and patient follow-up. In a 1:2 nested matching case-control study, we compared the outcome of cases with PIN alone with that of the control group. Each patient with PIN alone (16 patients) was matched randomly with 2 patients with benign prostatic hyperplasia (BPH) alone (32 patients) according to age (+/- 5 years) and serum PSA concentration (+/- 1 ng/mL).

Of 698 TURP specimens, 570 (81.7%) contained BPH and 128 (18.3%) contained adenocarcinoma and BPH. High-grade PIN was identified in 29 cases (4.2%), including 16 (2.8%) of those with BPH and 13 (10.2%) of those with cancer and BPH. Follow-up revealed adenocarcinoma in 3 of 14 patients (21.4%) with PIN and BPH only after 3, 5, and 7 years, respectively; mean follow-up for the 14 patients was 6 years (range 4 to 7 years), and none of the patients died of prostate cancer. Conversely, none of the patients (0%) without PIN in TURP specimens in the case-control study had subsequent adenocarcinoma.

The overall incidence of PIN in TURP specimens was 4.2%, including 2.8% without cancer and 10.2% with coexistent cancer. Prostatic adenocarcinoma was diagnosed within 7 years in 21.4% of patients with PIN in TURP specimen. Conversely, none of those without PIN matched for age and serum PSA had adenocarcinoma at follow-up. These results indicate that high-grade PIN is uncommon in TURP specimens and, when found, indicates a significant risk of cancer. The presence of PIN in TURP specimens should be reported by the pathologist; in addition, the entire specimen should be submitted for histologic examination to exclude carcinoma.