Why update the Gleason system?
Perhaps the most important reason to update the pathologic grading system for prostate carcinoma is that clinical practice in both urology and pathology has changed dramatically since Gleason first described his system. In Gleason’s era, an abnormal digital rectal examination was the most common indication for prostate biopsy, which was most often done with a large-bore needle. Consequently, almost 90% of men had large tumors with extraprostatic extension at initial diagnosis and less than 10% of patients had nonpalpable tumor diagnosed by transurethral resection.2 By contrast, the advent of PSA screening coupled with 18-gauge needle biopsies has led to the biopsy of smaller cancers and less tissue sampled per cancer, such that pathologists must assess tumor grade in small foci on thin cores, where it is more difficult to appreciate architectural pattern. In addition, greater sampling of the prostate and the presence of cancer on multiple cores bring the question of whether the highest
