A Model to Predict Prostate Cancer After Atypical Findings in Initial Prostate Needle Biopsy

Purpose: Atypical small acinar proliferation can occur alone or with high grade prostatic intraepithelial neoplasia in either a discontinuous or contiguous pattern in a prostate needle biopsy. We assessed whether different subgroups of atypical small acinar proliferation and high grade prostatic intraepithelial neoplasia denote a differing risk of detecting subsequent prostate cancer. Materials and Methods: We reviewed the pathological findings in 12,304 men who underwent initial prostatic needle biopsy during May 1999 to June 2007. Patients were included in the study if the initial diagnosis was atypical small acinar proliferation alone or combined with high grade prostatic intraepithelial neoplasia, or a benign diagnosis, and if followup prostatic needle biopsy was done. Results: Prostate cancer developed in 22%, 27% and 49% of patients in the benign, high grade prostatic intraepithelial neoplasia and atypical small acinar proliferation groups, respectively (p <0.0005). In all subgroups there was a 35% to 57% rate of prostate cancer detection. The prostate cancer risk increased in the atypical small acinar proliferation subgroups according to the extent of high grade prostatic intraepithelial neoplasia in the initial sample, with atypical small acinar proliferation associated with multifocal high grade prostatic intraepithelial neoplasia carrying a 71% prostate cancer risk. Conclusions: Atypical small acinar proliferation combined with high grade prostatic intraepithelial neoplasia, particularly when associated with multifocal high grade prostatic intraepithelial neoplasia, is associated with a significant risk of prostate cancer detection on followup biopsy.