In 1966, Donald F. Gleason, MD, PhD, first published a unique grading system for prostate cancer (PCa) based solely on the architectural pattern of the tumor, using a 5-point scale, where patterns 1, 2, and 3 represented tumors that most closely resembled normal prostatic glands, and patterns 4 and 5 were tumors showing increasingly abnormal glandular architecture (Table 1).