Prostatic "Capsule"?: Yea or Nay

[LADoc00]

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Okay....do people feel the prostate has a capsule? Albeit the fibrous CT is intimately associated with the stroma and is thin, am I behind the times in thinking some sort of capsule does exist?

Just had a debate with someone and I maybe actually wrong here. I know there are some anatomic pubs claiming there is no capsule, blah blah, but my gut inner-pathologist voice still believes there is one.


Is the prostatic capsule a Santa Claus or what??

 

[Cloaca]

Uhh...I'm confused. I thought there IS a prostatic capsule, at our program we assess for invasion THROUGH the capsule. Who says there isn't one and does it matter? If tumor is on the margin vs out of the "capsule" on the margin, isn't it the same thing?

 

[yaah]

There is a capsule, but it is incomplete in certain areas (mostly anteriorly), or at the very least hard to define. Thus, it depends on where you are asking about it. There is a capsule posterolaterally.

 

[LADoc00]

There is a capsule, but it is incomplete in certain areas (mostly anteriorly), or at the very least hard to define. Thus, it depends on where you are asking about it. There is a capsule posterolaterally.

Ok you saved my sanity here...I didnt just imagine there is a capsule then. whew..

I got completely blindsided as someone jumped on me with:
http://www.ncbi.nlm.nih.gov/pubmed/2909195

FROM:
Department of Pathology, University of Texas M.D. Anderson Hospital and Tumor Institute, Houston 77030.

Pathologic evaluation of tumor extent in a radical prostatectomy specimen for prostatic adenocarcinoma is extremely important in staging and planning further therapy. We studied whole-organ sections of 50 prostate glands, obtained at either radical prostatectomy for adenocarcinoma or cystoprostatectomy for bladder cancer, to evaluate the so-called capsule of the prostate, the prostatic apex, and the surgical margins. The outer surface of the prostatic portion of the specimen was totally inked with different colors for the anterior, posterior, left, and right areas. Cross sections were processed for histologic examination, and the apex (distal 1.5 cm) was amputated and radially sectioned (like a cervical cone). We found that the "capsule" is made up of a band of concentrically placed fibromuscular tissue that is an inseparable component of the prostatic stroma. The outer surface of this tissue gives rise to a few bundles of fibromuscular stroma that penetrate and disappear into the periprostatic connective tissue stroma. The apex is sparse in glandular elements, particularly in the anterior portion, and the outer fibromuscular layer is no longer present. Thus we conclude that the prostate does not have a true capsule, but only an outer fibromuscular band.

 

[KluverB]

I have been taught that the prostate does not have a true capsule. We do refer to tumor outside simply as "extraprostatic extension". This, in itself, is a little tricky in some parts of the prostate, especially anteriorly, where the smooth muscle bundles can be somewhat sparser, with some intervening adipose, and so what is "extraprostatic" becomes a somewhat subjective.

 

[DarksideAllstar]

Uhh...I'm confused. I thought there IS a prostatic capsule, at our program we assess for invasion THROUGH the capsule. Who says there isn't one and does it matter? If tumor is on the margin vs out of the "capsule" on the margin, isn't it the same thing?

Yeah, there's a difference-- pT3a if tumor goes out of the prostate into the fat vs there just being tumor in prostatic stroma at the margin pT2x.

And we are of the school of thought that there is a capsule.

 

[yaah]

I have been taught that the prostate does not have a true capsule. We do refer to tumor outside simply as "extraprostatic extension". This, in itself, is a little tricky in some parts of the prostate, especially anteriorly, where the smooth muscle bundles can be somewhat sparser, with some intervening adipose, and so what is "extraprostatic" becomes a somewhat subjective.

I think it's semantics. Whether you think the prostate has a true "capsule" or not, it has a dense connective tissue layer surrounding it laterally and posteriorly, so it acts like a capsule. It also acts as a barrier to spread of disease - very often you see tumor running up right against it but flattening out and stopping. That is why extraprostatic extension is important, and why perineural invasion is important (path of least resistance to get out, and once it gets out it spreads easier). And since most prostate cancers are posterolateral, this is important.

There was an article published entitled something like "anatomy of the anterior prostatic space" or something which explains the anterior anatomy well. It is hard to define extraprostatic extension at those sites - oftentimes you have to wait until it gets into thick skeletal muscle (not just individual fibers).

There have also been many articles published on the irreproducibility of defining extraprostatic extension.

 

[Gene_]

I think the fact that we report capsular invasion conveys to the clinicians that it is prognostically significant - it isn't. Because the capsule is incomplete and poorly defined, it's not surprising that invasion of it lacks significance.

 

[yaah]

I think the fact that we report capsular invasion conveys to the clinicians that it is prognostically significant - it isn't. Because the capsule is incomplete and poorly defined, it's not surprising that invasion of it lacks significance.

Invasion of the capsule where it exists does have significance. Those patients have a higher risk of recurrence. Invasion of the "capsule" where it doesn't exist is less significant, for the reasons you stated. Most "capsular invasion" is in areas where there is a capsule, because it is easier to define there (although still not very reproducible when focal).

 

[Gene_]

Invasion of the capsule where it exists does have significance. Those patients have a higher risk of recurrence. Invasion of the "capsule" where it doesn't exist is less significant, for the reasons you stated. Most "capsular invasion" is in areas where there is a capsule, because it is easier to define there (although still not very reproducible when focal).

I agree, somewhat, in that invasion THROUGH the capsule is significant, but I've yet to see a study where invasion INTO it proved to have prognostic significance. My hunch is that where the capsule is better defined, invasion through it, but not yet into the fat can be determined with some certainty. Thus, invasion through the capsule represents a progression of disease and can prove prognostically significant. However, if you're just guessing where the capsule is (which I have seen done often), that's obviously less scientific and not likely to prove significant in a study.