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The malignancy of prostate cancer depends not only on the type and extent of the tumor, but also on the extent to which the cells of the tumor tissue differ from the healthy prostate cells. The Gleason score assesses the extent and degree of tissue alteration. The higher the score, the more aggressive the tumor.
To determine the Gleason score, several tissue samples (biopsies) are first taken from the prostate and examined microscopically by the pathologist. Five "growth patterns" are distinguished based on the shape and arrangement of the prostate cells. 1 stands for well differentiated; the tumor tissue is still very similar to healthy tissue. In the case of a 5, the tissue has already de-differentiated to a large extent and only resembles the original tissue to a minor extent or not at all. There is a high degree of malignancy.
Cell patterns of the different Gleason scores:
Since tumor tissue is usually not homogeneous, two cell patterns are always assessed: The first number in the Gleason score indicates the cell pattern most frequently found in the tumor. The second number describes either the second most frequent or the most malignant pattern in this tumor area. The maximum Gleason score is 5+5=10 and the lowest nowadays is 3+3=6. A tumor is not classified as clearly malignant until a Gleason score of 6 (3+3) is reached.
Low Risk: Prostate tumors with a Gleason score of 6 (3+3) are the most common, occurring in about 50 percent of cases. They usually grow slowly. The formation of metastases in other organs and infiltration of the prostate capsule are very rare.
Intermediate Risk : Tumors with a Gleason score of 7 (3+4 or 4+3) are considered intermediate risk tumors.
High Risk: High risk tumors, with a Gleason score of 8 (4+4), 9 (4+5 or 5+4) and 10 (5+5) are highly aggressive tumors. They grow rapidly and in many cases infiltrate prostate capsule as well as adjacent organs in the pelvis. They metastasize early to lymph nodes and bone.