Gleason Grading System

Gleason grading system
Medical diagnostics
Gleason grade — Lower grades are associated with small, closely packed glands. Cells spread out and lose glandular architecture as grade increases. Gleason score is calculated from grade as described in the text.
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The Gleason grading system is used to help evaluate the prognosis of men with prostate cancer using samples from a prostate biopsy. Together with other parameters, it is incorporated into a strategy of prostate cancer staging which predicts prognosis and helps guide therapy. A Gleason score is given to prostate cancer based upon its microscopic appearance.Cancers with a higher Gleason score are more aggressive and have a worse prognosis. Pathological scores range from 2 through 10, with higher number indicating greater risks and higher mortality. A total score is calculated based on how cells look under a microscope, with half the score based on the appearance of the most common cell morphology (scored 1—5), and the other half based off the appearance of the second most common cell morphology (scored 1—5). These two numbers are then combined to produce a total score for the cancer.

Most often, a urologist or radiologist will remove a cylindrical sample (biopsy) of prostate tissue through the rectum, using hollow needles, and biomedical scientists in a histology laboratory prepare microscope slides for H&E staining and for diagnosis by a pathologist. If the prostate is surgically removed, a pathologist will slice the prostate for a final examination.

A pathologist microscopically examines the biopsy specimen for certain "Gleason" patterns. These Gleason patterns are associated with the following features:

In the present form of the Gleason system, prostate cancer of Gleason patterns 1 and 2 are rarely seen. Gleason pattern 3 is by far the most common.

A pathologist then assigns a grade to the observed patterns of the tumor specimen.

The pathologist then sums the pattern-number of the primary and secondary grades to obtain the final Gleason score. If only two patterns are seen, the first number of the score is that of the tumor's primary grade while the second number is that of the secondary grade, as described in the previous section. If three patterns are seen, the first number of the score would be the primary grade and the second number the pattern with the highest grade. For example, if the primary tumor grade was 2 and the secondary tumor grade was 3 but some cells were found to be grade 4, the Gleason score would be 2+4=6. This is a slight change from the pre-2005 Gleason system where the second number was the secondary grade (i.e., the grade of the second-most common cell line pattern).