Prostate Biopsy and the Gleason Score: What You Should Know
Deciphering the Results
Biopsied tissue is sent to a laboratory, where a pathologist views the cells
under a microscope. When healthy cells become cancerous, their appearance
begins to change. The more altered the cells look, the more dangerous the
cancer is likely to be.
The results from a prostate biopsy are usually given in the form of the
Gleason score. On the simplest level, this scoring system assigns a number from
2 to 10 to describe how abnormal the cells appear under a microscope. A score
of 2 to 4 means the cells still look very much like normal cells and pose
little danger of spreading quickly. A score of 8 to 10 indicates that the cells
have very few features of a normal cell and are likely to be aggressive. A
score of 5 to 7 indicates intermediate risk.
A careful, detailed look at the biopsy results gives your doctor an even
more precise picture of what’s happening in your prostate, says Michael Morris,
MD, an oncologist at Memorial Sloan-Kettering Cancer Center in New York. For
each biopsy sample, pathologists examine the most common tumor pattern and the
second most common pattern. Each is given a grade of 1 to 5. These grades are
then combined to create the Gleason score. For example, if the most common
tumor pattern is grade 2, and the next most common tumor pattern is grade 3,
the Gleason score is 2 plus 3, or 5. Because the first number represents the
majority of abnormal cells in the biopsy sample, a 3 + 4 is considered less
aggressive than a 4 + 3. Combined scores of 8 or higher are the most aggressive
cancers. Those under 6 have a better prognosis.
It's important to remember that the Gleason score is assigned by a
pathologist viewing cells under a microscope. Although the grading system has
been shown to be reliable, it is not perfect. It depends on the skill of the
pathologist observing the cells. For that reason, doctors may sometimes order a
follow-up biopsy if they have any doubts or questions about the results.