The Gleason score is a rating system that was developed to rate the severity of prostate cancer. By judging the microscopic appearance of the cells extracted from a biopsy of the prostate, physicians determine how advanced the cancer is. The more a cancer cell looks like a normal cell, the less severe the case is. Cells that lump together in a shapeless mass are more malignant, and thus more severe. The Gleason score differentiates these degrees of mutation into five grades. By looking at the two most prevalent patterns of cancer cells in a biopsy, a physician determines the Gleason Score by adding the two together. For example, if your two most prevalent patterns of cell mutation both rank as ones on the Gleason Scale, your score would be two, which is the lowest score possible. Scores of four or below represent slow-growing prostate cancer. Scores between seven and 10 represent high grade prostate cancer. For more information about the Gleason Score, contact a cancer specialist in your area.