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Grading & Staging Prostate Cancer

How is prostate cancer staged?

What are the stages and grades of prostate cancer?

A healthy prostate gland has uniformly shaped and sized cells across the entire gland. The cells are organized in a precise and specific pattern. When there is a malignancy (cancer), cells appear abnormal. Cancer cells will continue to grow and divide outside the body’s normal balance of cells. This may cause a tissue mass to form, commonly known as a tumor.

After initial blood tests, a biopsy is performed to confirm the diagnosis. Taking a sample of tissue from the prostate, a pathologist examines the sample using a microscope. The pathologist is looking for cells patterns to determine if cancer is present, and if so, what the level or grade of abnormality is. In other words, how severe the cancer present is. The most common system used for grading prostate cancer is called the Gleason system. Gleason scores range from 2 to 10, with 10 being the most severe. A low-grade tumor is one that is slow-growing and is still confined within the prostate. In contrast, a high-grade tumor is much more aggressive, faster-growing, and has a higher likelihood of spreading beyond the prostate, known as metastasizing.


All About Gleason Scores

With the Gleason system, the pathologist examines the tissue sample and looks to identify the two most prevalent cells patterns in the tissue. Each pattern is given a grade from 1 to 5. Lower grades of 1 to 3 identify less aggressive forms of cancer. These types of cancer more than likely have not metastasized. The higher grades of 4 or 5 indicate a more aggressive cancer that has a much higher likelihood of metastasizing or having already spread.

The two grades are combined to form the Gleason score. If only one cell pattern is present, the grade is added to itself to form a Gleason score.

The lower range of scores is considered to be between 2 and 4. Again, these lowest grades indicate very slow-growing cancer. These cancers typically haven’t metastasized and don’t pose a significant health risk most of the time. Grades between 5 and 7 are considered to be in the intermediate range. The highest grades between 8 to 10 pose the most serious health risk. These aggressive cancer forms have a much higher potential to metastasize outside the prostate.

Prostate Cancer Staging

The grading of prostate cancer determines how aggressive the cancer is likely to be and the likelihood of it spreading beyond the prostate. Staging of prostate cancer looks at the size of the area affected by cancer and how far the cancer may have spread both within the prostate and beyond. The grade of the tumor combined with the stage of the cancer and the patient’s PSA level help doctors determine what the best course of treatment is.

Prostate Cancer Staging: What the Numbers Mean

TNM Description
T1 Tumor isn’t detectable in imaging exams or a DRE, but there are cancerous cells present.
T1a Some cancer has been detected, but the sample shows less than 5% is malignant, and it is considered low-grade.
T1b Similar to above but more than 5% of the tissue sample is malignant or may not be low-grade.
T1c Through a needle biopsy, PSA results were found to be elevated, they aren’t palpable.
T2 DRE detected a tumor, but the tumor is confined to the prostate gland.
T2a The tumor detected is confined to the prostate gland and is within one-half or less of one of the prostate lobes.
T2b The tumor isn’t present in both lobes but is confined within more than one half of a lobe.
T2c The tumor has been detected in both prostate lobes but hasn’t spread beyond the prostate.
T3 Locally extensive.
T3a Cancerous cells have moved beyond the prostate capsule from one or both lobes.
T3b Prostate cancer is detected in the seminal vesicle.
T4 Cancerous cells are found in organs adjacent to the prostate.
T4a The tumor has spread to the bladder neck, and/or outside the urinary sphincter, and/or rectum.
T4b Cancerous cells have spread to areas close to the prostate gland.
N The lymph nodes are involved.
NO No cancer has been detected within the lymph nodes.
N1 The cancer found within the lymph nodes has a measurement of 2 cm or less.
N2 Cancer is found in one or more lymph nodes, and the measurements range between 2 cm and 5 cm.
N3 Cancer is found in one or more lymph nodes, and the measurements are greater than 5 cm.
M The cancer has metastasized to distant sites other than the lymph nodes.
MO The cancerous cells have been confined to the prostate, surrounding tissue, and pelvic lymph nodes only.
M1 Cancerous cells have metastasized beyond the pelvis and include bones, lungs, and/or other regions.


Prostate Cancer Stages

There are four distinct stages that categorize prostate cancer.

  • Stages I and II – These are the early-stages cancer where cancerous cells have not spread outside the prostate and show no signs of spreading.
  • Stage III – Cancerous cells are found outside the prostate in nearby tissue. Cancer could have spread to the seminal vesicle, which is the gland behind the prostate that helps to produce semen.
  • Stage IV – Cancerous cells have spread outside the prostate to nearby tissues and distant sites like lymph nodes and/or organs.

Tumor Growth Stages

Localized –

Stage I or A or T1: Tumors can’t be felt under an examination.

Stage II or B or T2: Tumors that can be felt under examination but are confined to the prostate gland.

Regional –

Stage III or C or T3: Tumors have spread beyond the prostate capsule and can be present in the seminal vesicle, located behind the prostate.

T4: The tumor exists in nearby muscles and organs.

Metastatic –

Stage IV or D and N+ or M+: Tumors have spread to other parts of the body. N+ indicates that tumors have spread into the lymph nodes. M+ refers to tumors when they have spread to other parts of the body.

Each of these stages is identified based on several systems. The most common system for staging is called TNM. TNM determines the size of the tumor and exactly how far it has spread. Another common system is an ABCD rating system used to characterize the tumor.

How is prostate cancer staged?

There are three main exams used in the clinical staging process for prostate cancer. The Digital Rectal Exam (DRE) and a Prostate Specific Antigen (PSA) tests are covered under the Testing for Prostate Cancer section. The third exam, a transrectal ultrasound (TRUS), is covered here.

TRUS utilizes an ultrasound probe to visualize the area on a screen by inserting it into the rectum. Additional exams are ordered, like a bone scan, if the staging indicates that the cancer has spread beyond the prostate or is in the lymph nodes. The bones are one of the most common locations prostate cancer metastasizes to, so bone scans are particularly useful because they determine whether that is the case.

Bone scans are completed by creating images of bones on film or a computer screen. A tiny amount of radioactive material is injected into a blood vessel. It then travels through the bloodstream until it reaches the bones, which collect it and where it is detected by a specific scanner.

If a patient is not reporting any bone pain or their PSA levels aren’t over 10nc/ml than bone scans are not typically ordered. Without these particular markers, it is very unlikely that the cancer has metastasized to the bones.

What is primary cancer?

The term primary cancer simply refers to the original tumor site. It can start anywhere in the body.

What is metastasis and how does it happen?

Metastasis is when cancer spreads beyond their original tumor. Cancer cells detach from the primary cancer site cell divisionand are absorbed into the lymphatic system or the bloodstream. The lymphatic system produces and delivers cells that fight infections throughout the body. Once the cells are in these systems, cancer cells are spread to other areas of the body.

Cancer cellsOnce the cancer cells have spread to other areas, they can cause a new tumor to develop in other locations. The cells in any new tumors are derivatives of the original tumor. For example, if the primary site was breast cancer, no matter where the other tumors develop, they are still made from breast cancer cells and will present the same cell patterns under a microscope.

Questions you should be asking your doctor.

It’s always good to research your diagnosis, but ultimately, because cancer is so situational-specific, the best information will be obtained from having a conversation with your medical team. The best strategy for getting your questions answered is to start a list, writing them down as you think of them and then bring that list with you to your appointments. Don’t be afraid to ask clarifying questions if you don’t understand any answers you receive. Some of the most common questions men have about prostate cancer are below:

  • I have these symptoms, are they related to prostate cancer?
  • With my particular situation, what tests do you recommend and why?
  • If my symptoms aren’t related to cancer, what can I do to reduce them and/or manage them?
  • If I am diagnosed with cancer, what is the grade and stage?
  • What level is my PSA and what was the increase from my last visit?
  • Do you recommend that I see another pathologist to get a second opinion?
  • Are there any other tests to see if the cancer has metastasized?
  • What are the treatment options you recommend, and what are the benefits of each treatment?
  • What is your experience performing these specific procedures?
  • Are there any side effects associated with these treatments and what are they?
  • Are there any appropriate clinical trials that would benefit me to participate in?
  • What is my prognosis, given the grade and stage of my cancer?
  • Is a recurrence anticipated?