Like staging, grading levels are also assigned to prostate cancer cases. Grading takes place after a biopsy (removal and examination of tissue) is done. The tissue samples are sent to a laboratory for analysis by a pathologist, a doctor who specializes in diagnosing disease by looking at these samples.
If cancer is present, the pathologist will assign a grade for the cancer. The grade refers to the cancer's appearance and indicates how quickly a cancer is growing. Most pathologists grade prostate cancer according to the Gleason score, which assigns a grade from 1 to 5 based on how the cancerous cells look compared to normal prostate cells.
Grade 1. The cancerous tissue looks very much like normal prostate cells.
Grades 2 to 4. Some cells do look like normal prostate cells, others do not. Patterns of cells in these grades vary.
Grade 5. The cells appear abnormal and do not look like normal prostate cells. They appear to be scattered haphazardly throughout the prostate.
The higher the Gleason score, the more likely it is that the cancer will grow and spread rapidly. Pathologists often identify the two most common patterns of cells in the tissue, assign a Gleason grade to each, and add the two grades. The result is a number between two and 10. A Gleason score of less than six indicates a less aggressive cancer. A grade seven and up is considered more aggressive.
Other Test Results
Sometimes, when a pathologist looks at the prostate cells under the microscope, they don't look cancerous, but they're not quite normal, either. These results are often reported as "suspicious" and fall into one of two categories, either atypical or prostatic intraepithelial neoplasia (PIN).
PIN is often further divided into low grade and high grade. The significance of low-grade PIN in relation to prostate cancer remains unclear. Many men have it when they are young and never develop prostate cancer.
Biopsy results that fall into either atypical or high-grade PIN are suspicious for the presence of prostate cancer in another portion of the gland. There is a 30% to 50% likelihood of finding prostate cancer in a later biopsy when high-grade PIN is initially discovered. For this reason, repeat biopsies are generally recommended.