Grading of prostate cancer: Evolution and changing concepts

Grading system for prostatic cancer (PC) was first described in1966 by Dr. Donald Gleason. Over the years, histologic, clinical diagnosis and management of PCa have evolved, leading to revisions of the Gleason system first by the International Society of Urological Pathology (ISUP) in 2005 and more recently in 2014. Unlike the original Gleason score (GS) ranging from 2 to 10, the current system no longer assign Scores 2–5, the lowest score being 6. The new grading system of 2014 proposed Five Grade Groups based on revised GS which produces a smaller number of grades with the most significant prognostic differences and may contribute to a decrease in the overtreatment of low-grade PC detected by prostate-specific antigen screening. This review provides an update on the evolution and revision of the Gleason grading system, with a discussion on the deficiencies, benefits, and limitations of the revised and new grading system of ISUP 2005, 2014, and 2019.