00:01
Okay. Again, with our broad brush
thinking about benign versus malignant.
00:06
What is being shown here is a uterus with
attached fallopian tubes and ovaries,
everything's labeled there and we're
going to compare benign leiomyoma,
a smooth muscle tumor of the
uterus that's quite common,
otherwise known as fibroids.
00:20
And we're going to compare that
with malignant leiomyosarcoma,
in terms of the features.
00:25
Again, by way of a review,
of deciding what's benign, what's malignant.
00:30
So, benign leiomyomas, again, an
“Oma” of the “Leio-myo” cells,
which are the smooth muscle cells,
it's small, tends to be small, but it can be big,
they tend to be extremely well
demarcated with a capsule around them,
because they are slow growing
and they're non-invasive.
00:49
And with the exception that
I mentioned previously,
of that benign metastasizing leiomyoma,
they are not metastatic.
00:56
Then again, keep in mind, there are
exceptions to everything I’m telling you,
I’m lying all the time here.
01:01
And they also tend to be very well differentiated,
if you look at them histologically,
it looks like smooth muscle, anywhere
else in the uterus, so that's benign.
01:12
In contradistinction, when we think
about malignant leiomyosarcomas,
so, a mesenchymal tumor of
these smooth muscle cells,
they tend to be large as is indicated here,
they tend to be very poorly demarcated,
they are invasive, they are not encapsulated,
they are rapidly growing with
hemorrhage and necrosis as is shown,
because they are compressing
and otherwise outgrowing their vascular supply.
01:38
They tend to be locally invasive,
but they also tend to induce metastases
by getting in to veins or lymphatics
and the vein being shown
here has got a tumor cell,
that's escaped from the primary tumor
and is going to go someplace else and set up shop
and they also tend to be
very poorly differentiated,
they do not necessarily look
like the smooth muscle cells,
that they were derived from.
02:04
An important caveat here, most, in fact,
the vast majority of benign tumors,
do not convert into malignant tumors.
02:15
So, fibroids are incredibly common,
these leiomyomas incredibly common,
but almost never, do they
turn into leiomyosarcomas.
02:27
The leiomyosarcomas that occur in the uterus,
tend to be de novo mutations,
that cause that malignant tumor.
02:35
But there really isn't a pathway
from benign to malignant,
in the smooth muscle cell lineage
or in a lot of other tumors,
where there are benign versions.
02:45
So, for example the lipoma,
that we talked about before,
benign fat cell tumor, almost never,
almost never converts into a liposarcoma.
02:56
Okay and with that we've come to
the end of benign versus malignant
and hopefully you're not totally confused.