When a biopsy confirms the presence of prostate cancer, the tumor is examined under a microscope and categorized into grades. Those grades and PSA levels can be confusing. This section will help explain what these measurements mean.

PSA (Prostate-Specific Antigen)

PSA is a substance produced by the prostate. In the absence of prostate disease, PSA is generally found in the blood at a very low level. Elevated PSA readings can be a sign of prostate cancer or a non-cancerous prostate condition.

Grade

The grade, also called a Gleason grade, indicates how different the cancer cells are compared to normal cells, when seen through a microscope. A Gleason grade ranges from 1 to 5. A Gleason grade of 1 means the cancer cell clusters resemble normal prostate tissue. If the cancer cells have little or no resemblance to normal prostate cells, the cancer may get a Gleason grade of 5.

Because prostate cancers often have areas with different grades, a doctor will examine the two areas that make up most of the cancer. A grade is then given to each of the two areas. These two grades are added together to yield a Gleason score of between 2 and 10.

Low Gleason grades and scores generally indicate slow-growing cancer. High grades and scores indicate a cancer that is likely to grow aggressively.

Staging

Your doctor may also talk to you about the stage of the cancer. Staging is the assessment of the size and location of prostate cancer (that is, how far the cancer has already spread). Staging is necessary to help you and your doctor decide what type of treatment is most appropriate.

Currently there are two different systems used to stage prostate cancer. The traditional method classifies the disease into four categories, rated A through D. The second system is called TNM, which stands for Tumor-Nodes-Metastases.

A-D Staging

In this type of staging, Stage A is considered to be early cancer. The tumor is located within the prostate gland and cannot be felt during a DRE.

In Stage B, the tumor is considered to be within the prostate and can be felt during a DRE.

In Stage C, prostate cancer is more advanced. Stage C indicates that the tumor has spread outside the prostate to some surrounding areas, but not to lymph nodes or other organs. This stage of cancer can be detected by a DRE.

In Stage D, the cancer has spread to the nearby lymph nodes and usually to distant sites, such as the spine, ribs, or other bones or organs.

TNM Staging

The initials TNM stand for Tumor, Nodes, and Metastases. TNM staging takes into consideration tumor stage (T) and whether the cancer has spread to lymph nodes (N) and metastasized (M) to distant sites in the body.

Tumor stage is assessed on a scale of 1 to 4.

Generally, tumors graded T1 are confined to the prostate gland but are so small that they cannot be felt during a DRE or detected during ultrasound.

T2 prostate cancer is confined to the prostate, but it is large enough to be detected during a DRE.

T3 and T4 prostate cancers have expanded beyond the prostate into surrounding tissues.

Lymph node involvement is graded on a scale of 0 to 3. N0 (N zero) means that the cancer has not spread into the lymph nodes. The cancer will be considered N1, N2, or N3 depending on the number and size of lymph nodes involved.

Metastasis is rated 0 or 1. M0 (M zero) means no metastasis has occurred; M1 indicates metastasis to a distant location.

Learn about treatment options for prostate cancer and its symptoms.