The Gleason score is a system of grading prostate cancer. The system was named after Donald Gleason (1920–2008), the American pathologist who developed it with other colleagues in the 1960s.
Grading and Differentiation
The Gleason score consists of five grades, and is measured on a scale of 1 to 5. The score denotes the differentiation of the cancer cells when viewed under a microscope.
Grades 1 and 2
Grades 1 and 2 closely resemble normal prostate tissue. In these stages, the glands are small, well formed, and closely packed. However, in Grade 2, the tissues begin to develop larger glands and wander away from each other.
Grade 3 is the most-common grade. At this stage, the cells begin to grow darker and vary in shape, and leave the glands to invade surrounding tissue.
In Grade 4, the gland unit begins to disintegrate as increasingly more cells invade the surrounding tissue.
Grade 5 signifies the lowest-differentiation grading of the cells. At this stage, glands are rendered unrecognizable, and attempts to form new gland units are completely abandoned.