Prostate cancer diagnosed after initial biopsy with atypical small acinar proliferation suspicious for malignancy is similar to cancer found on initial biopsy.

OBJECTIVES: To compare matched clinical and prostatectomy data between (a) men with an initial biopsy diagnosis of atypical small acinar proliferation (ASAP) suspicious for malignancy whose cancer was diagnosed subsequently, and (b) men with a cancer diagnosis not preceded by an ASAP diagnosis. ASAP diagnoses apply to 1.5%-9.0% of prostatic biopsies and predict definite cancer in about 45% of repeat biopsies.

METHODS: At our hospitals, during overlapping intervals from 1990 to 2001, 7081 men underwent prostate biopsy, and 227 (3.2%) had an overall diagnosis (based on all cores sampled) of ASAP. We concurred with the ASAP diagnosis in 184 cases (81%). Repeat biopsy was performed in 129 (57%), with 22 again having ASAP and 51 (40%) adenocarcinoma. Nineteen men underwent prostatectomy at our hospitals. The controls comprised men who underwent prostatectomy before and after each man with an initial ASAP diagnosis (2:1 match with cases). Findings included grade, pathologic stage, measured maximum dimension of tumor, resection margin status, patient age, and latest preoperative serum prostate-specific antigen.

RESULTS: Men in the initial-ASAP group did not differ significantly from controls with respect to age (63 vs. 61, P = 0.08). Initial-ASAP and control groups had serum prostate-specific antigen levels of 5.9 and 7.4 ng/mL (P = 0.32), respectively; mean Gleason scores were 6.2 and 6.6 (P = 0.11); mean stages were pT2b and pT2b; and tumor size averaged 0.9 and 1.2 cm (P = 0.36). Fewer men with initial-ASAP diagnosis on biopsy had positive margins (5%) than did those in the control group (30%, P < 0.05).

CONCLUSIONS: An ASAP diagnosis represents undersampled cancer in at least 40% of cases and places men at risk of prostate cancer with similar clinicopathologic findings as in other men with cancer.