What is Prostate Cancer Cell Leakage and Microscopic Capsule Penetration?

Prostate cancer goes through three basic steps in growth.

Prostate Cancer Growth Step 1:

The first step is a growth inside the prostate gland. For a long period of time, prostate cancer grows only inside the prostate and is contained by the capsule that surrounds the prostate. Think of a shell around an egg.

Prostate Cancer Growth Step 2:

Eventually, the second step occurs – prostate cancer cell leakage through the capsule so that cancer grows next to but outside the prostate, which is officially called microscopic capsule penetration.

Now think of a hole in an eggshell with the yolk leaking out. If the growth outside the prostate is large enough, it can be felt on prostate examination (the DRE), which would make the prostate cancer a stage T3, but this is very uncommon. Almost all capsule penetration cancer is microscopic. If left alone, the third step will eventually occur.

Prostate Cancer Growth Step 3:

Step 3 is the spread of prostate cancer (metastasis) beyond the prostate area to lymph nodes, bones, lungs, or any other place in a man’s body. Depending upon the treatment method, prostate cancer can still be cured in Step 1 or Step 2. With rare exceptions, prostate cancer is not curable in Step 3.

What is Microscopic Capsule Penetration?

Microscopic capsule penetration is one of the most important concepts for understanding prostate cancer and has been extensively studied at Johns Hopkins University. Prior to surgery (Radical Prostatectomy), 5,629 men had a prostate biopsy, PSA, and were staged either T1 or T2 based on DRE (digital rectal exam). Surgical removal of the prostate was performed on these men.

The whole prostate was then given to the pathologist for microscopic examination to determine, among other things, if cancer cells had leaked through the capsule and were outside the prostate, which means that men were really stage T3. The chance of cancer cell leakage was then correlated with Gleason score, stage, and PSA in the Partin tables. However, it is impossible to know whether or not a man has microscopic capsule penetration before any treatment. Microscopic cancer cell leakage through the capsule cannot be detected by any test, CT scan, MRI scan, or x-ray before treatment.

Figure 1. The three steps of prostate cancer growth.

3 Steps of Prostate Cancer Growth

Figure 2. Close-up of microscopic capsule penetration (cancer cell leakage) seen with the microscope.

Microscopic capsule penetration

How Do Prostate Cancer Cells Leak Through the Capsule and Outside the Prostate?

Cancer cell capsule penetration can occur in four basic ways (Fig. 3). The first way is through the development of cancer adjacent to the capsule, with the cancer simply destroying the capsule (eating a hole in the capsule) and leaking out. Again, think of egg yolk leaking through a hole in the eggshell. A second way is through perineural invasion, which means cancer cells travel along branches of the sex nerve and “tunnel” through the capsule to escape the prostate. The third method of microscopic capsule penetration can occur when cancer cells are located at the bottom (apex) of the prostate because there is no prostate capsule in this location, which makes it easy for cancer cells to escape the prostate in this area. Check your pathology report to see if you have cancer at the apex because this is the most common place for positive surgical margins, meaning cancer cells are cut across and left behind after Radical Prostatectomy. The fourth method is an invasion into the seminal vesicles, which are attached to the top of the prostate.

Figure 3. Four ways for cancer leakage to occur.

4 Ways for Cancer Leakage to Occur

What is Perineural Invasion for Prostate Cancer?

The finding of perineural (meaning “around the nerve”) invasion helps identify a greater chance of cancer cell leakage through the capsule to outside the prostate (called microscopic capsule penetration) and a lower cure rate. A man has two sex nerves. One runs along the right side of the prostate and the other along the left. Branching off these two large nerves are many smaller nerves that go through the prostate capsule or shell in a “tunnel” and enter the prostate. The smaller nerves have a space around them called the perineural space. Cancer cells in the prostate can get in the perineural space and use it as a “tunnel” to travel and escape through the capsule and grow and spread outside the prostate.

Figure 4.Perineural invasion: a common pathway for cancer cell leakage where the cancer “tunnels” along the space around the sex nerve through the capsule

Perineural Invasion

What is my Chance of Having Microscopic Capsule Penetration?

We can look this up in the Partin tables. For your particular case of prostate cancer with a Gleason score of 4+3=7, PSA 4.3, and stage T1c, your chance of having microscopic capsule penetration is 40%. So, you actually have a 40% chance that your cancer has progressed to step 2 growth and that you have T3 cancer, not T1c.