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Grading & Staging Prostate Cancer

How is prostate cancer staged?

Prostate Cancer Grading & Staging

What are prostate cancer grades and stages?

Healthy cells of the prostate are evenly shaped and sized across the board and highly organized in the pattern consistent with a healthy gland. However, in the presence of a malignancy, cells lose this healthy appearance. And as cancer cells continue to grow and divide, a tissue mass may develop, known as a tumor.

Prostate cancer is identified through a biopsy of prostate tissue. Once a tissue sample is taken through biopsy, it is examined under a microscope by a pathologist. It is the responsibility of the pathologist to assign each piece of tissue with a grade that defines the level of abnormality of the cells. The most often-used system for grading when it comes to prostate cancer is the Gleason system.

Using this system, the scores can range from 2 to 10. A low-grade tumor is defined as a slow-growing tumor that has not moved beyond the prostate itself. A high-trade tumor, however, is a faster growing, more aggressive tumor with a higher likelihood of metastasizing or growing beyond the prostate.


Understanding Gleason Scores

Through the Gleason grading system, the pathologist who examines the tissue is responsible for first identifying the two biggest areas of cancer that reside in the tissue. These particular grades range from 1 to 5 with the lower grades (1 to 3) identifying the least aggressive forms of cancer. These lower grades typically have not metastasized. The higher grades of 4 and 5 are more aggressive forms of cancer and have a higher likelihood of spreading or having already metastasized.

The grades assigned to these two areas of cancer are then added together to produce the official Gleason score. Lower scores are 2 to 4 which are considered low-grade – these are slow-growing cancers that have not moved past the prostate and typically pose no significant health risk.

Intermediate grade cancers are 5 to 7. And high-grade cancers with scores of 8 to 10 are more aggressive forms of cancer with a higher possibility of spreading beyond the prostate.

Prostate Cancer Staging

Separate from grading which identifies the growth rate of your cancer and the chance of it metastasizing, staging determines the size of the cancer area and how far it may have spread – both in the prostate itself and beyond the prostate.

Together, a tumor grade and stage – along with a patient’s PSA level – allows doctors to determine the most appropriate treatment plan.

Prostate Cancer Staging: What the Numbers Mean

TNM Description
T1 Cancerous cells are present, but a tumor is not detectable in DRE or on imaging tests.
T1a Cancer has been found incidentally, but less than 5 percent of a sample is malignant and is deemed low-grade.
T1b Cancer has been found incidentally with more than 5 percent of a sample deemed malignant and/or not low-grade.
T1c PSA results are elevated, but not palpable, found via a needle biopsy.
T2 The tumor is detectable in DRE, but is confined to the gland.
T2a A detected tumor is confined to no more than half of one of the prostate’s two lobes.
T2b The tumor is confined to more than one half of one lobe, but is not detected in both lobes.
T2c The tumor is evidenced in both lobes of the prostate, but has not yet spread beyond the prostate capsule.
T3 Locally extensive.
T3a Prostate cancer has penetrated the prostate capsule on one or both lobes.
T3b Evidence of prostate cancer exists within the seminal vesicle.
T4 Tumor spread evidenced in adjacent organs.
T4a Cancer has been found within the bladder neck and/or the rectum and/or the outside of the urinary sphincter.
T4b Cancer has spread to other areas near the prostate gland.
N Lymph node involvement.
NO Cancer has not been detected in the lymph nodes.
N1 Cancer has been found within one or more lymph nodes with measurements of 2cm or less.
N2 Cancer has spread to one or more lymph nodes and measures at 2cm to 5cm.
N3 Cancer that measures greater than 5cm that has spread to one or more lymph nodes.
M Distant site metastasis has been discovered in locations other than lymph nodes.
MO Cancer is confined within the prostate, pelvic lymph nodes and surrounding tissues.
M1 Cancer has spread beyond the pelvis to include lungs, bones and/or other areas.


Stages of Prostate Cancer

Stages I and II – These early stages of cancer have not spread beyond the prostate and show no signs of metastasizing.

Stage III – Refers to cancer that can be found beyond the outer layer of the prostate where it has spread to nearby tissues. At this stage, cancer may also have spread to the seminal vesicles, the gland behind the prostate that is responsible for helping to produce semen.

Stage IV – This is cancer that has spread beyond the prostate to nearby tissues as well as organs and/or lymph nodes.

Stages of Tumor Growth

Localized –

Stage I or A or T1: Refers to non-palpable tumors (tumors that cannot be felt upon examination).

Stage II or B or T2: Refers to palpable tumors (tumors that can be felt upon examination but still remain restricted to the prostate gland).

Regional –

Stage III or C or T3: Defines tumors that have grown beyond the outer layer of the prostate gland (the prostate capsule) and may even be present in the seminal vesicles, the gland that contributes to semen production and is located behind the prostate.

T4: Refers to the existence of tumor in nearby organs and muscles.

Metastatic –

Stage IV or D and N+ or M+: Refers to tumors that have spread (metastasized) to other parts of the body. N+ identifies those tumors that have spread to regional lymph nodes and M+ identifies those tumors that have metastasized to other parts of the body.

These specific stages are identified using several staging systems. One of the most commonly used systems is known as TNM which is used to determine the size of the tumor and how far the tumor has spread. Another staging system that is often used is a rating system that characterizes a tumor by assigning it an ABCD rating.

How is prostate cancer staged?

The main tests used for clinical staging of prostate cancer are a Digital Rectal Exam (DRE), Prostate Specific Antigen (PSA), and transrectal ultrasound (TRUS). Extensive information can be found about DRE and PSA under the Testing for Prostate Cancer section.

TRUS uses an ultrasound probe inserted in the rectum to visualize the area on a screen. When clinical staging suggests that cancer has spread to the lymph nodes or beyond, additional tests may be ordered including a bone scan. A bone scan helps determine if the prostate cancer has spread to the bone which is a common location for metastasizing prostate cancer.

A bone scan is a technique that creates images of bones on a computer screen or on film. During a bone scan, a small amount of radioactive material is injected into a blood vessel and travels through the bloodstream where it collects in the bones and is detected by a scanner.

However, a bone scan may not be ordered if the patient is not experiencing any bone pain and does not present with a PSA level over 10 ng/ml. It has been shown that these particular markers mean that the patient is very unlikely to have cancer that has spread to the bones.

What is primary cancer?

Primary cancer refers to the site of the original tumor location (organ, tissue, etc.). Primary cancer can start in any area of the body.

What is metastasis and how does it happen?

When cancer spreads it is known as metastasis. During metastasis, cancer cells detach from the original tumor or cell divisionprimary cancer site. These cancer cells are then absorbed into the bloodstream or lymphatic system (which produces the cells that fight infection and delivers them throughout the body). Traveling through these systems, cancer cells are spread to other locations throughout the body.

Cancer cellsThis movement of the cancer cells to other parts of the body can cause a new tumor to development in these other locations. No matter where the tumor develops the cells that make up this tumor derive from the original tumor location or primary cancer. So if the original cancer is breast cancer, even if the cancer spreads to other parts of the body, it is still made up of breast cancer cells and will present as such under a microscope.

Important questions to ask your doctor.

Reading up on your diagnosis is a great idea and always encouraged. But in the end, there’s nothing that can replace the information gained through a conversation with your doctors. Keep a running list of questions that you can easily add to as you think of them and bring them along to your appointments. If you don’t understand the answer that you are given, ask for clarification until you are comfortable. Here are some of the common questions that are asked by men about prostate cancer:

  • Are my symptoms consistent with the signs of prostate cancer?
  • What are the recommended tests in this particular case? Why do you recommend them?
  • If my symptoms are not cancer, what can I do to manage them appropriately?
  • If this is a cancer diagnosis, what is the stage and grade?
  • What is my PSA level?
  • Would you recommend that I get a second opinion from another pathologist?
  • Are there any additional recommended tests to determine if the cancer has metastasized?
  • What are the treatment options available to me and what are the benefits of each?
  • How much experience do you have performing these particular procedures?
  • What are the side effects associated with each treatment? If I choose this treatment option, how can these potential side effects be managed?
  • Are there any clinical trials in which it would be appropriate for me to participate?
  • What is the prognosis for my grade and stage of cancer?
  • Do you anticipate any recurrence?