A prostate biopsy removes small amounts of tissue to
examine under a microscope to determine whether cancer is present. Typically
between 6 and 12 biopsies are taken of the prostate using a core biopsy needle.
By examining tissue samples under a microscope, the diagnosis of cancer can be
established. When a tumor is discovered, it is classified by grade. 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 cells to normal prostate cells.
- If the cancerous cells appear to resemble the normal prostate tissue very
closely, they are said to be very well differentiated and are considered to be
Gleason grade 1. 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 very
different from the normal prostate cells, then they are very poorly
differentiated and are assigned a Gleason grade 5. (It is rare to see a
Gleason grade 1 or 2 cancer.)
- Because prostate cancer tissue is often made up of areas that have different grades, the pathologist will closely examine the areas that make up the largest portion of the tissue. Gleason grades are then given to the two most commonly occurring patterns of cells. They will describe and rate the cancer cells in two ways: (1) how the cancer cells look and (2) how they are arranged together.
Once the two grades have been assigned, a Gleason score can be
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 =
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).
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