The Gleason Scale – How Prostate Cancer Is Graded

Once prostate cancer has been diagnosed, it’s important for the doctor to be able to judge how widespread the cancer is and how aggressively it might grow. With this information, the doctor will be able to decide what the prognosis for the disease is, and what sort of treatment is necessary. To do this, physicians use a tool called the Gleason scale to classify the state of the disease.

The Gleason scale is named after pathologist Donald Gleason, who invented it in the 1960s. To use it, the doctor takes a biopsy of the affected part of the prostate, and a pathologist will examine it under the microscope. The Gleason scale runs from 1 to 5, with 1 being almost normal and 5 being severe. Type 3 is the most common form of prostate cancer.

The pathologist who examines the biopsy will assign two Gleason grades, one for the larger part of the sample and one for the smaller part. The numbers together provide a Gleason score from 2 to 10, which provides a rating of how aggressive the prostate cancer is expected to be.

The Gleason grades represent the following arrangements of normal and cancer cells:

1: “Well-differentiated.” The cancerous glands are small and uniform, and don’t look very different from normal prostate glands.
2: Similar to 1, but the glands are larger, more irregularly shaped, and farther apart.
3: The glands have turned a darker color, and in some cases, the cancer cells have left the glands and begun to spread to surrounding tissue.
4: “Poorly differentiated.” The prostate glands have mostly disappeared, replaced by lumps of cancerous cells that are spreading throughout the tissue.
5: No glands are visible, only cancer cells that are usually spreading aggressively, forming sheets throughout the prostate tissue.

Gleason scores are usually given as two numbers, such as 3+2. Remember, the first number represents the larger part of the sample, so a score of 4+1 represents a case of prostate cancer that’s more aggressive than 1+4. So it’s always best to ask your doctor for both gradess that make up your Gleason score so you have the clearest possible picture of your prostate cancer.

A Gleason score of 6 or below is usually considered to be low-grade cancer, while a score in the 8-10 range is a severe, high-grade cancer.

If you decide to have your prostate removed, the pathologist will be able to examine the entire gland after the surgery and gain a more complete overview of the state of your cancer. This may lead to your receiving a different Gleason score from the one calculated on the basis of the biopsy.