Prostate biopsy is the only test that can confirm the diagnosis. Tissue from the prostate is viewed underneath a microscope. Biopsy results are reported using something called a Gleason grade and a Gleason score.
The Gleason grade is how aggressive the prostate cancer might be. It grades tumors on a scale of 1 - 5, based on how different from normal tissue the cells are.
Often, more than one Gleason grade is present within the same tissue sample. The Gleason grade is therefore used to create a Gleason score by adding the two most predominant grades together (a scale of 2 - 10). The higher the Gleason score, the more likely the cancer is to have spread beyond the prostate gland:
- Scores 2 - 4: Low-grade cancer
- Scores 5 - 7: Intermediate- (or in the middle-) grade cancer. Most prostate cancers fall into this category.
- Scores 8 - 10: High-grade cancer (poorly-differentiated cells)
There are two reasons your doctor may perform a prostate biopsy:
- Your PSA blood test is high. See also: PSA
- A rectal exam may show a large prostate or a hard, irregular surface. Because of PSA testing, prostate cancer is diagnosed during a rectal exam much less often.
The PSA blood test will also be used to monitor your cancer after treatment. Often, PSA levels will begin to rise before there are any symptoms. An abnormal digital rectal exam may be the only sign of prostate cancer (even if the PSA is normal).
The following tests may be done to determine whether the cancer has spread:
