(UroToday.com) Prostate cancer diagnosis is predicated on needle biopsy. Histopathologic examination of prostate biopsy specimens is both necessary for diagnosis and to risk-stratify patients with prostate cancer, based on assessment of tumor grade and volume. Despite the key role in assessment of prostate biopsies to guide treatment decision making, there are considerable limitations in the accuracy of grading on the basis of intra-tumoral heterogeneity, inter-observer variability, and other factors.