• 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. The patterns of cells in these grades vary.
  
  
• Grade 5: The cells do not look like normal prostate cells and appear to be scattered haphazardly throughout the prostate.
  
  

The higher the score, the more likely it is that the cancer will grow and spread rapidly. A grade is often given to the two most common patterns of cells in the prostate tissue, and both numbers are added together. A grade less than 6 indicates a less aggressive cancer. A grade 7 and up is considered more aggressive.

Sometimes don't look cancerous under a microscope, but they're not quite normal either. These results are often reported as "suspicious." They generally fall into two categories, either atypical or prostatic intraepithelial neoplasia (PIN).

PIN is often divided into low grade and high grade. The importance of low-grade PIN in relation to prostate cancer is still unclear. Many men have it and never develop prostate cancer.

But with atypical findings or high-grade PIN, cancer may already be present somewhere else in the prostate gland. For high-grade PIN, there is a 30% to 50% chance of finding prostate cancer on a later biopsy. For this reason, repeat prostate biopsies are often advised.