Gleason Score (or Gleason Sum)

 

Prostate cancer is a heterogeneous tumor and more than one Gleason grade is often seen. A Gleason score (GS) was originally defined as the sum of the two dominating patterns, i.e. the most common + the second most common. This has been modified for needle biopsies (ISUP 2005) so that the GS always includes the highest grade, even when it is a minimal component.

 

The GS is a strong predictor of prognosis. It correlates with outcome on active surveillance and after radical prostatectomy or radiotherapy.