What is the Gleason system for grading prostate cancer?
A pathologist named Gleason described the grading system for prostate cancer. The Gleason grade reflects how aggressively the prostate cancer is likely to behave.
The pathologist will look at the biopsied prostate tissue under a microscope to compare the cancerous tissue to normal prostate tissue.
How are the Grades interpreted?
If the cancerous cells appear to resemble the normal prostate tissue, they are said to be very well differentiated and considered to be Gleason grade 1 to 3. This means that the tumor is not expected to be fast growing. On the other hand, if the cells in question look fairly irregular and different from the normal prostate cells, then they are poorly differentiated, and are assigned a Gleason grade of 4 to 5. (It is rare to see a Gleason grade 1 or 2 cancer.)
The prostate cancer tissue is often made up of areas that have different grades; therefore, the pathologist will closely examine the areas that make up the largest portion of the tissue. Gleason grades are given to the two most commonly occurring patterns of cells. They will describe and rate the cancer cells in 2 ways: (1) how the cancer cells look and (2) how they are arranged together.
Once the two grades have been assigned, a Gleason score is determined. This is done by adding together the two Gleason grades. The resulting Gleason score will be a number from 2 to 10. (i.e., 3 + 4 = 7/10)
The biopsy also can give important information about whether the cancer involves small nerves within the gland (perineural invasion) and an indication of how extensive the cancer might be within the gland (number of cores positive).
Stage refers to the amount of cancer in the prostate, and whether the cancer has spread outside the gland. There are several tests that may be useful in determining tumor stage, but for most men no such tests are required. This is because the chance of finding cancer elsewhere in the body is so low for most men with early cancers of the prostate that such tests are not warranted.