When we talk about the pathophysiology
for the development of colonic polyps,
we're really talking about the same
pathways that are operative
when we talk about the development of
colorectal cancer and you have seen
or I will refer you to other areas in the collection of Lecturio lectures
that talks specifically about colorectal cancer.
Okay. The epithelium at baseline has a normal
regulated turnover. The cells are born.
They grow and they die over
the course of three to seven days.
So, you'll get the entire sequence of events that completely
replaces the colonic epithelium every week or so.
If you have a germline mutation in one of the genes such as APC
that regulates normal colonic epithelium proliferation,
that gets you started down a path that
the epithelium is completely normal.
You may then get a second hit in a similar
gene or the same gene.
So, that means that you have a germline
mutation and that gene is non-functional.
And then, one of the cells happens to get
a second hit in the other normal gene.
And now, you have loss of heterozygosity
and that can drive the mucosa to proliferate abnormally.
Now, we have mucosa at risk.
With further additional mutations and a proliferating epithelium, you may still stochastically acquire a mutation say,
in KRAS or other genes that are proto-oncogenes
that drive cellular proliferation from another pathway.
And then, we are going to develop adenomas.
So, these cells have lost some of their normal behavior.
They are not yet cancers but they are proliferating.
They are proliferating in a setting
where there may be additional opportunities
for mutations and they acquire additional changes.
So, they may have mutations in p53,
the normal gene that's going to identify
abnormal chromosome or DNA structure and repair it.
They may have changes in methylation.
They may have changes in cyclooxygenase.
All these things can potentially drive the acquisition of mutations
that will eventually allow these to become malignant.
The clinical presentation for colonic polyps.
How do these colonic polyps present?
Well, they may be completely asymptomatic.
In fact, the vast majority of them are only
discovered when you have screening colonoscopy.
But they may present in other ways.
So, they are epithelial proliferations overlying blood vessels
and if you erode the epithelium,
you may get blood.
Or you may have a production of mucus because of irritation
or because the epithelium is making more mucus
and you may see that in the stool.
If the polyp is sufficiently large,
it may actually mechanically obstruct the bowel lumen.
So, the patient may present with constipation.
On the other hand, you may have local irritation that drives
increased bowel motility and patients may have diarrhea.
And then, with larger polyps beyond just
constipation, you may have intussusception.
You may have the polyp drag as the peristaltic
wave goes by, pull the bowel proximally to distally
and you have telescoping or intussusception.
How do we make the diagnosis?
have no manifestations detected by
either you or your patient.
So, let's talk about diagnosis which can be
a little bit of a challenge since most of these
colonic polyps really don't have much
in the way of manifestations.
So, it's largely by screening colonoscopy or other forms of colon cancer
evaluation that we're going to detect polyps early.
For people who have average risk which is to say
they don't have a family history of polyps
or of colorectal cancer, colon screening
will begin roughly at the age of 45.
If you have a first degree family member
with colorectal cancer at an age less than 60 years
where there's a family history of colonic polyps,
then, you will get screened beginning a little bit earlier.
For patients who are at higher risk, so, we know
inflammatory bowel disease is a risk for polyps
and colorectal cancer and the polyposis syndromes
that we had talked about, Lynch and FAP,
all of those mean those individuals
need to be screened very early.
And at some cases like FAP where there's 100%
risk of developing colon cancer over a lifetime,
you may elect to not screen and just remove
the colon earlier rather than later.
So, for patients where you suspect a hereditary
polyposis or colorectal cancer syndromes,
you may do formal molecular testing, particularly,
if an individual has been identified in the family,
you will test all first degree relatives.
For regular screening, you'd want to look for occult blood
and there are a number of tests, including some
that you can get through the mail
and over the counter that looks specifically
for common DNA mutations in the stool.
And then, finally, the gold standard by
which we're going to make the diagnosis
and we're going to do the appropriate
polyp removal for evaluation
and/or prevention of cancer
is going to be sigmoidoscopy
if you're just looking in the more
distal sigmoid or colonoscopy.
And in fact, I would say, for the vast majority of
your patients, you're not going to stop at the sigmoid.
You're going to want to look all the way
around over to the cecum.
So, with colonoscopy screening, we're going to be able to establish
a relative risk of the development of colon cancer.
So, depending on what we find, we can tell patients,
"You have this risk. You have that risk."
If there are no adenomas, there is still a lifetime
risk of about 3% of developing colorectal cancer
but in most cases, that's a good sign.
If on colonoscopy, we found one to two adenomas
and all of them are less than a centimeter,
that's a lifetime risk of colon cancer of about 5%.
If on the other hand, we find high risk
adenomas, a serrated type adenoma
or if we can't find villous adenomas,
that increases the risk of colon cancers.
The lifetime risk goes up somewhere
between 15 and 20%.
This is an example of just what you can see
when you become your - a world famous gastroenterologist
and put the colonoscope up and take a look.
So, on the left is a polyp on a stalk,
so, called pedunculated polyp.
This overall size here, it's hard to estimate,
but it's about 1.5 centimeters.
So, it's not too - the four centimeter category
where we would have a high index
of suspicion for malignancy.
But it's something if we don't take it out overtime
will acquire additional mutations and become malignant.
On the right-hand side is showing multiple polyps
in a colon and even though these are small,
this raises the specter of a familial polyposis syndrome,
so, Lynch syndrome or familial adenomatous polyposis.
Hyperplastic polyps have just
benign epithelial proliferations.
So, it's just a little outpouching of mucosa
and the histology is totally benign
and I'm not expecting you as a medical student
to say, "Oh, yeah. That's benign.
I would know of that in a - " No, you don't have to.
That's why you send it to me.
But that's an example of
what you can see and note,
when we do the biopsy, we're not
getting a full thickness biopsy.
In fact, you don't want to do that because that
would mean you perforated the bowel.
This is just an epithelial biopsy.
This is a histology of a juvenile polyp.
So, this is a benign hamartomatous polyp and it's classically
associated with increased mesenchymal elements.
That's why we have all that spaced out
stuff and they're cystically dilated glands.
So, this is a completely benign
Now, we're going to get into the category
however of things that are not so benign.
So, this is an adenomatous polyp.
This is probably a tubulovillous. It's got a little bit of both.
It's kind of tubular architecture but it's
also a little bit kind of fibular or villous.
On the left-hand side, we're looking at
a sessile polyp that's kind of stuck down.
It looks like a slug there in the colon
and then, a tubulovillous polyp
on the right cutting cross-section
which has big frond-like projections.
Again, making the distinction between tubulovillous, tubularvillous,
etc. is a microscopic finding for the most part.
And an adenomatous polyp has a greater density of cells.
They tend to be more hyperchromatic.
The nuclei tend to come off the basic membrane.
The glands may be more dysmorphic and the cells
may have some degree of atypia.
This would be a relatively
small adenomatous polyp.
There's no malignancy in here but if we don't take it out,
we're at risk for this eventually progressing to malignancy.
And now, management.
And management really is all about
what you find on your first colonoscopy
and then, time to the next one.
So, when we do colonoscopy, we do assume that it's
a complete exam all the way to the cecum.
You can have polyps anywhere in the colon and just
stopping in the sigmoid is not going to be sufficient.
You want to make sure that you have
an adequate prep or preparation
so that you have cleaned out the colon sufficiently
to be able to see all of the real estate.
And then, we want to make sure the person
who's actually doing this is skilled
so that they can recognize a
polyp when they see one.
So, a normal colonoscopy is associated with a 0.5% risk
of colorectal cancer in the succeeding 10 years.
There is still a lifetime risk of about 3%
but it's a very low risk.
So, if you have a normal colonoscopy, no adenomatous polyps,
even if you have small hyperplastic polyps,
you are good to go for about a decade and
you'll come back in 10 years and we'll do it again.
If you have low risk adenomas, so, you have
one to two of them. They're less than a centimeter.
The dysplastic, the changes that make them
worrisome in terms of low-grade, high-grade, etc.
dysplasia, they're all low-grade,
you repeat in 7 to 10 years.
So, almost as good. If they are the sessile serrated
type and they're a certain number
and they're less than a centimeter,
you can repeat that in 5 to 10 years,
depending on your degree of comfort.
And if there are other findings,
so, if there are three, more than three
adenomatous polyps even though they're small.
If there is large hyperplastic polyps, in that case,
you would probably repeat in 3 to 5 years
and if there is advanced neoplasia or high-risk adenoma,
more adenomas, 5 to 10 or sessile polyps,
or morphology with greater than a centimeter in
size and the histology has a villous component
and it's high-grade dysplasia, you're going to want
to get that patient back in 3 years.
And if there are more than 10 adenomas,
you want them back in a year.
You do not want to let them go and at that time,
you've plucked out all the adenomas that you saw.
You didn't leave any behind but they're at risk
of developing malignancy if you let them go longer.
What is being shown on the slide here
is a colonic resection for a large polyp.
So, you may go in on your primary,
your subsequent evaluations on colonoscopy,
see something that you just can't pluck out.
That requires then calling your favorite
neighborhood surgeon and they will come in
and usually do an open procedure
to take out the polyp.
If you see also lymphovascular invasion,
that's another indication on histology
that you need to have a larger resection
to make sure that there is no nodal metastasis.
With that, we've covered benign and
malignant polyps and what to do about them.