The total Gleason score (GS) is determined by adding the two most predominant morphological
grade patterns together. For example a GS of 5+2 = 7 means that final GS is 7 (PC is at an
intermediate stage), with the most prevalent glandular structure being poorly differentiated, while the
second most abundant glandular structure was quite well differentiated. However, if the GS was 2+5
= 7, the most prevalent structure would be well differentiated (GS = 2) meaning that this type of
prostate tumor has less aggressive features compared to the previous tumor. Overall, high-grade
prostate tumors (GS > 8) are more likely to spread and grow quickly compared to low-grade prostate
tumors (GS < 6). (Humphrey 2004).