Histological slide (H & E stain at x300) showing prostate cancer. On the right is a somewhat normal Gleason Value of 3 (out of 5) with moderately differentiated cancer. On the left is less normal tissue with a Gleason Value of 4 (out of 5) that is highly undifferentiated. The Gleason score is the sum of the two worst areas of the histological slide. Photographer: Otis Brawley
