The grade of prostate cancer refers to how the cancer cells look under a microscope. Identifying what grade your cancer is helps you and your doctor choose the best way to treat it.

Prostate cancer cells are either well-differentiated, moderately differentiated, or poorly differentiated. Differentiation is a term that is used to describe how different the cancer cells look from normal cells under a microscope. Well-differentiated cancers have very clear boundaries and cells that look relatively normal. They usually do not grow and spread rapidly. Poorly differentiated cancers have less clearly defined boundaries and cells that look very abnormal. They often grow and spread rapidly.

After your cancer has been looked at under a microscope, your doctor can tell you what grade your cancer is.

Gleason score

Prostate cancer is often graded using the Gleason score, on a scale of 2 to 10. The Gleason score is considered a powerful tool for predicting how aggressive a tumor will be.¹ The higher the Gleason score, the more likely the tumor is to grow rapidly and spread (metastasize) to other parts of the body.

• A Gleason score of 2 to 6 indicates well-differentiated tumors with cells that are expected to grow slowly and not spread readily.
• A Gleason score of 7 indicates moderately differentiated tumor cells.
• A Gleason score of 8 to 10 indicates poorly differentiated tumors with cells that are likely to grow rapidly and spread to other parts of the body.

Rarely, the following system is used to grade cancer:

• GX: Grade cannot be determined
• G1: Well-formed, normal cells (Gleason score 2 to 4)
• G2: Mostly normal cells (Gleason score 5 to 7)
• G3: Poorly formed cells with many traits of cancer cells (Gleason score 8 to 10)