Okay. We're going to put on
the hat of a pathologist now.
We're going to try to distinguish
between benign and malignant tumors.
And it's not trivial, in fact that
would be the job of pathologists,
who have many, many years of training
and so, the goal here is not to turn
you into card-carrying pathologists,
but rather to think about, the various
aspects that make something benign,
I’ll say right up front that, benign
tumors might be a cause of death,
so, for example a benign meningioma,
in the brain that grows and grows and grows,
could compromise normal vascular
structures and you can die from that.
On the other hand, there
are many malignant tumors,
even if you don't treat them or make
them go away, will not kill you,
so, many skin cancers, squamous
cell carcinoma with the skin,
basal cell carcinoma with the
skin, are malignant tumors,
they have molecular and genetic instability,
but they typically will not kill you.
So, the difference between benign and malignant,
is not about whether it's
fatal or not, important point.
Okay, first of all though we have to
talk about how we name these things.
So, tumors contain proliferating
neoplastic cells and supporting stroma,
that's all part of what they are
and then we want to name them,
kind of based on whether we think they're
benign or we think they're malignant
and the features of each will
become clear as we go further along.
In general, for benign tumors,
if we're going to name them,
we will give them the cell of origin,
so, if it comes from an
adipocyte, it will be a “Lipo.”
If it comes from a chondrocyte,
making cartilage it's a “Chondro.”
If it comes from a bone-forming
cell, it's an “Osteo.”
And we take those cells of origin and
then add “O-M-A” at the end an “-oma”
and that's our way of saying we
have a benign lipoma or a lipoma,
a benign tumor of the adipocytes
or chondroma, a benign tumor of the chondrocytes,
an osteoma, a benign tumor of osteocytes.
You can also have benign skin tumors, a papilloma,
so, that's generally our
way of assigning benignancy,
meaning that it's not going to be something
that we have to worry too much about.
However, like everything else in medicine,
there are exceptions and an important
set of exceptions are shown here.
Melanoma, “Melan” means it
comes from a melanocyte,
and the “-oma” you would think,
“Oh my God,” that's a benign tumor of melanocytes,
no, it's a wildly malignant
tumor. So, there are exceptions.
Similarly, mesothelial-oma, mesotheli
part, is from mesothelial cells
and you'd say, “Oh my God,” that's
a benign mesothelial cell tumor,
well, no, it's a malignant tumor.
So, the nomenclature that has been
used and developed over the years
and ever since pathology started doing
things, isn't always completely uniform,
and actually, everything I’m going
to tell you in this particular talk,
it's lies, it's all lies, because
there are always exceptions.
But if you can kind of remember
the basic ground rules,
you'll be right 99% 95% of
the time, something like that.
So again, another example of a violation of this
kind of, cell of origin and -oma
being benign, is a lymphoma.
Lymphocytes forming a tumor, well
it turns out lymphoma is malignant,
so again, a bad name but we're stuck with it.
Seminoma, is just another one.
Seminomas are malignant tumors,
of the of the seminiferous tubules
and those are always malignant.
Again, you would say, “Oh my God” it's
semin-oma, it's benign, no, it's not,
so, we just have to live with that.
Okay, on the malignant side of the equation.
For epithelial tumors that are malignant,
we will call them, “Carcinomas” and you're saying,
“Well, okay you're telling me lies
again this ends with an -oma.”
Yes, it does, but the
“Carcin” on the front of that,
indicates that it's cancer already, okay,
and just because it ends in
-oma doesn't mean it's benign,
so, that carcinoma means
it's an epithelial malignancy
and then we will put things on the front of that.
We will say, it's a squamous cell carcinoma,
from squamous cell differentiation,
or it's an adenocarcinoma, coming
from glandular differentiation.
The fact that we have “Carcinom”
on the front of that, means that,
it is malignant,
even though it ends in -oma.
So, go shoot me or shoot the
pathologists that develop this.
We will also identify, we may say
that is it a pathocellular carcinoma,
meaning it comes from liver cells
or it is a hemangioendothelioma,
which means it comes from endothelial cells.
It's just the way you're going
to have to learn to live with it.
Then there are mesenchymal
tumors, so these I mean again,
I know that this means it's malignant,
you now know because I'm
telling you these are malignant.
Mesenchymal tumors are called sarcomas, again,
“It's oh my God it's ending with -oma,
you told me that was benign.”
Well okay, but it's the
“Sarc” on the front of that,
that makes it a malignant tumor.
So, if you have a benign tumor
of fat cells, that's a lipoma.
If you have a malignant tumor of fat
cells that's a liposarcoma, okay.
If you have a benign tumor of
chondrocytes, that's a chondroma.
If you have a malignant tumor of chondrocytes,
that's a chondrosarcoma and that's how
we make that particular distinction.
Other malignant names, that we
have to deal with is lymphoma,
we've already talked about that is
a malignant tumor of lymphocytes
and leukaemia’s means that
it's a malignant tumor of
circulating blood elements
and although “Leuk,” is actually a
root word meaning white blood cell,
we will use that term leukaemia,
when we talk about other blood-borne malignancies.
And then melanocytes forming a melanoma,
we've already talked about that as well.
So, some of this makes some
sense, some of this is,
“Gosh you're telling me lies.”
I think as you go along you will
quickly be able to parse out,
when we say something is benign, versus malignant
and how we can distinguish that.
And you'll quickly know that
melanoma, mesothelioma, lymphoma,
seminoma those are malignant.