So, types of neoplasms.
And it runs the gamut from at the top benign,
to at the very bottom, metastatic.
So, you can have pre-malignant
You can have in situ malignant dysplasia,
high-grade dysplasia, which is
basically, in situ carcinoma.
You can have invasive malignant tumors
and you can have metastatic tumors.
Importantly, most benign tumors and
we've talked about this previously,
but most benign tumors,
say like a lipoma or a leiomyoma,
do not become malignant.
It's usually a separate cell,
that starts going through a clonal expansion,
acquires additional mutations.
Most of the time if you have a mole,
a benign nevus on your skin,
it's not going to turn into a malignant melanoma.
All right, so the vast majority
of benign tumors never go bad.
So, how do I establish a diagnosis?
What are the things that I need to do?
On the right-hand side is
just a well to moderately
with a substantial number of inflammatory cells.
The adenocarcinoma are those
around that mucinous core
and I know, I can say that, this is in the lung,
pretty with great assurance,
because there's also anthracotic pigment,
the black pigment down on
the lower right-hand side.
There is some desmoplastic response
and there are signs of tumor cell focal necrosis,
say at the very bottom.
When I get a specimen,
in any surgical specimen
I first need to determine,
that I have an adequate amount of
material to do what I need to do.
Now, this is a fairly big chunk, that
came out of a partial pneumonectomy,
but sometimes I get little tiny cores,
basically, fine needles,
that pull out maybe 50 cells,
I may not have adequate tissue to
render an appropriate diagnosis.
I definitely as a pathologist,
read the clinical history,
I cannot make a diagnosis in the absence of that.
It's important for me to know the gender,
the age, the site where
things are being sampled etc.
Also, any past medical history, past exposures,
because all of those can potentially influence,
what I'm seeing down the microscope.
And sometimes, if I know
through the clinical history,
the patient has had lots of radiation.
Some very funny-looking cells,
that I see under the microscope,
actually, just be a typical
fibroblast and not tumor.
Whereas, if this same patient
who has not been radiated
and I have some very funny-looking cells,
maybe even with a few other features,
I could say well maybe that's a fibrosarcoma.
So, clinical history,
is actually very important part
of the pathologic diagnosis.
I have to do a macroscopic exam,
I have to look at the entire
piece of whatever I have
and determine margins and determine location
and determine size, etc., etc.
So, a macroscopic exam is part of my diagnosis,
clearly the microscopic exam
is a very important part,
there are many things I can see down a microscope,
that are not apparent at any other level.
I will need to run in many cases ancillary tests,
I'll do immunohistochemistry,
I might do electron microscopy,
I will do molecular diagnostics,
I might do cytogenetics.
So, there are other things that will help me,
establish the very best diagnosis,
for my surgical or oncology colleagues.
And then I have to put the whole story together.
So, everything that you see above there,
all those six boxes,
I need to put together into a coherent diagnosis
and be able to convey that,
as well as my interpretation of everything,
to the oncologist or the surgeon.
So, what kind of tricks can I do as a pathologist?
There are a whole bunch of ancillary technologies,
that we can apply, to tissue.
So, first of all, we can do
the traditional staining,
this the top panel is showing an
H&E a hematoxylin and eosin staining
of an adenocarcinoma,
that's what the pointer, the arrow is pointing to,
is a little cluster of adenocarcinoma cells,
they're actually signet ring cells,
with mucin pushing the nucleus off to the side,
surrounding it, is a whole
collection of, lymphocytes.
But when I look at this, I don't
know whether that clearing,
adjacent to the nucleus and the tumor cells is,
mucin or is it glycogen, is it fat,
that all makes a difference in terms
of what kind of cell that might be.
So, then I can do in the bottom
panel a mucicarmine stain.
A mucicarmine stain, is, the
mucus, that kind of pink color,
so, I'm able to identify just
on a variety of special stains,
what's going on.
I can also do enzyme histochemistry.
So, some cells have an
intrinsic enzymatic activity
and for example, in acute myelogenous leukaemia,
which is being shown here,
there is brown pigmentation in the cells,
due to the activity of the
myeloperoxidase present in the AML cells.
So, if I add on a substrate for
myeloperoxidase, I get this brown pigment
and that's another way that I can determine,
what I'm dealing with.
In some cases, we go to electron microscopy,
so, you're seeing an image of a
transmission EM of a tumor cell,
this happens to be a breast cancer cell,
has a very prominent nucleolus, open chromatin,
but sometimes on EM,
there will be features that will allow us to say,
“Oh, this differentiation pattern
is more like say skeletal muscle
and features that we might not ever see,
on the regular routine histochemistry.”
We can do a variety of immunohistochemical stains.
This is where I'm taking an
antibody against a specific entity.
That antibody is coupled to an
enzyme that I can then measure,
by adding on appropriate substrate.
So, everything that's brown
that you're seeing here,
is because an antibody bound
to a particular antigen.
In the top panel, is a cytoplasmic antigen,
so, this could be a cytokeratin or this could be
some other component that is unique
and intrinsic to a particular cell.
So, for example, cytokeratin 7, is a cytokeratin,
that's normally found in tumors
that originate above the diaphragm.
CK20, is a cytokeratin that's
found in malignancies that occur,
below the diaphragm.
So, if I'm not sure where this came from,
I can do a CK7 and a CK20 stain and
be able to determine between the two.
The bottom panel is showing an antibody
directed against the transcription factor
and often, there may be an
upregulation of a transcription factor
associated with certain tumors.
In this particular case, I
believe, that this is, a TTF-1.
So, it's a thyroid transcription factor
1, that is associated with thyroid
and lung cancers and there's a very
market upregulation in that tumor
and I see it within the nucleus,
because that's where all good
transcription factors should go.
So, using these immunohistochemical tricks,
I can very nicely ascertain cell of origin
and be able to point clinicians
in various directions.
We can also do in situ hybridization.
This is where we take, nucleotide
probes that look for specific
portions of the DNA.
What's shown up above is an
oncogene over expression,
where there is too much of the red signal,
indicating for example that this
could be a MYC over amplification,
(MYC) MYC over amplification,
so that's just an example.
But we can also use it to see
whether there is a translocation,
so, normally, say there's one
gene over here, on one chromosome
and another gene over here on another chromosome
and I can put in a probe that
stains green for that one
and red for that one,
normally in every cell, I'd see a
separate green dot and a separate red dot.
If, however I see the red and green dots together,
I know that I've had genetic translocation
and now fusion of those two chromosomes
bringing the two signals together
and that frequently happens in a number of tumors,
for example, the BCR/ABL
translocation that occurs,
in chronic myelogenous leukaemia.
We can do a cytogenetic analysis.
These are very, very cool.
You basically can paint each
chromosome with its own unique color
and that's what you're
seeing on the left-hand side,
is that we're seeing all those
various chromosomes, that are painted.
What shouldn't happen, unless
there are translocations, is that,
you shouldn't have two colors on one chromosome
and several of the chromosomes in there have,
multiple colors on one bar.
That means that there have
been numbers of translocations
and knowing what color,
goes with which chromosome,
I can say exactly what
translocations have occurred.
I can also do this just on a metaphase smear
and that's what on the lower right.
Is just a metaphase smear of chromosomes
and we can with various banding staining patterns,
be able to identify, what
translocations have occurred.
We can also do flow cytometry, which is,
basically, taking antibodies,
coating single cells,
running them past a laser scanner that says,
that cell is positive for that particular marker
or negative for that particular marker,
we do that all the time for
leukaemia’s and lymphomas,
to determine clonality.
And then finally, in the 21st century,
we are doing a lot of molecular diagnostics,
we're doing DNA sequencing,
deep DNA or RNA sequencing,
to get signatures of mutations,
to identify over-amplifications
or loss of heterozygosity.
All of those things are going
to be part of my toolkit,
in making diagnoses.