Pitfalls: Chest, Part 1

Initial Nodule Quiz

I'm gonna start with a quick question here.

This is not something you need to respond to,
but these are two different patients
with two different nodules.

One nodule is benign and one is malignant.

And I'd like you to just choose in your head which one you think is a cancer.

And the cancer is that one.

Now, the nodule that you're seeing on your
left is dense.

It's homogeneously opaque, it's irregular and speculated
and associated with some satellite nodules.

And I think it was just some sort
of little focal pneumonia and it went away.

The nodule on your right is a cancer
and many nodules that you see,
or many cancers that you see are of ground glass opacity
as the nodule that was displayed on that image.

In a study here done as part
of a lung cancer screening evaluation,
ground glass opacity nodules that were seen on CT 60%
or so were malignant nodules
that were mixed ground glass opacity and solid.

About half were malignant
and nodules that were solid, like
that dense nodule I just showed you.

Only 11% were malignant.

And overall 75% of cancers were of ground glass opacity
or mixed ground glass opacity and solid.

Adenocarcinoma Diagnosis Quiz

Now, here is that case again,
and I'd like you to respond to this question.

What is the most likely diagnosis for this nodule?

And you have four choices.

The answer is adenocarcinoma in situ.

And will we be getting those numbers?

There we go.

Wow, response.

No, that's fine. That's exactly the result I wanted.

This is what I wanna do is talk about adenocarcinoma,
pulmonary adenocarcinoma
and adenocarcinoma is responsible
for about half of lung cancers.

It usually presents as a lung nodule
and adenocarcinomas account for 60 to 70%
of lung cancers presenting as a solitary nodule.

The incidence of this tumor seems to be increasing,
and this is the tumor that is less commonly associated
with smoking than other cell types of cancer.

World Health Organization 2004 Classification

Now, in 2004, the World Health Organization
classified pulmonary adenocarcinoma as consisting
of three primary types.

The first being bronchi alveolar carcinoma,
BAC non-invasive tumor coming in non mucinous
and mucinous subtypes, invasive adenocarcinoma
with several cell types where the tumor is invading lung.

And then in between those two is a mixed subtype
of adenocarcinoma that has both components
of BAC and invasion.

Now in this classification, they determined that a BAC
or bronchi alveolar carcinoma had to be characterized
by pure lepidic growth.

And it usually appears on CT as a nodule
of ground glass opacity, sometimes with solid components.

And it's usually the non mucinous cell type of adeno.

And if the tumor is less than three centimeters at
diagnosis, five year survival, basically a hundred percent.

Now this is lepidic growth.

Lepidic growth is non-invasive tumor growth using alveolar
walls as a scaffold.

And you can see on the bottom half of the slide,
tumor cells are growing along the alveolar walls,
but they're not destroying lung.

You can still see alveoli, there's no invasion.

And lepidic by the way, means relating to scales
or a scaly covering layer,
and the cells are lining the alveolar walls,
I guess like scales on a fish or on reptiles
or something of that sort.

Now here's another example of a ground glass opacity,
solitary nodule patient that has obvious emphysema
and a hazy ground glass nodule on the right upper lobe.

And using that World Health Organization classification,
this would be classified as a BAC with lepidic growth.

And this again, what lepidic growth would
look like for a nodule.

And you can see why a nodule that has this pattern
of growth would be of ground glass opacity.

There's still lots of air within it.

This is the other end of the spectrum, a patient
with a solid and speculated nodule representing an
invasive adenocarcinoma.

You can see that this tumor in the histology is invading
lung and destroying lung, and there's areas of necrosis
and cavitation and speculation
because of surrounding lung fibrosis.

And then in between those two extremes is the mixed subtype
of adenocarcinoma where you see both ground glass opacity
and a solid center.

So these were the three types of adenos
that were described in the World Health Organization
Classification in 2004.

2011 Reclassification of Pulmonary Adenocarcinomas

Now, a year or so ago, this article threw
that all into the dumpster.

This is a paper that was published by an international group
in the Journal of Thoracic Oncology
and they reclassified pulmonary
adenocarcinomas and of interest.

You can see that this paper has about 48 authors,
as I recall, and it's 41 pages long
and it's published as a concise review.

Now what this article has indicated or,
or has given to us is a total reclassification
and renaming of these cell types of tumors.

BAC three centimeters
or less in size with pure lepidic growth
is now termed adenocarcinoma in situ,
five year survival. A hundred percent mixed subtype
of adenocarcinoma three centimeters
or less with lepidic growth.
And five millimeters
or less of invasion is now termed minimally invasive
adenocarcinoma or MIA mixed subtype
with lepidic growth.

And more than five millimeters
of invasion is now termed lepidic predominant adenocarcinoma,
LPA five year survival a little lower than the other types.

And then invasive adenocarcinoma has remained the same.

So what we used to call BAC now has these other names.

A few years ago I would've called that case a BAC
that I showed you, I probably did.

Now it would be called adenocarcinoma in situ
because it was a ground glass opacity nodule
with no obvious soft tissue.

Now this is Prince. I'm sure you'll all remember Prince.

Now, at some point in his career, Prince stopped referring
to himself as Prince
and started referring to himself with a symbol.

Now, this made it difficult for the media
to talk about Prince on the air or in writing
because how do you say that?

Simple? Well, what they came up with
is the artist formerly known as Prince or TAFKAP.

So he was referred to in print and on TV as TAFKAP.

Now this is that tumor again, this is the adenocarcinoma,
formerly known as BAC
or TAFKAP, BAC no longer exists
as terminology you should be using.

You should be using the new terminology.

And that's the first pitfall I'm going
to talk about or have talked about.

Pitfalls in Ground Glass Opacity Nodule Reporting

So here's a ground glass opacity nodule.

It's pure ground glass.

It was followed three months later it looks the same.

So it's not something transient.

You have to worry about this being an adenocarcinoma.

And this would be dictated as consistent
with adenocarcinoma, most likely adenocarcinoma in situ.

Now here's a tumor, a ground glass opacity nodule
with five millimeter,
a less than five millimeter solid center.

You can see there's a little solid tissue in the
center of that ground glass.

This will be dictated as consistent with adenocarcinoma,
most likely minimally invasive adenocarcinoma.

And here's one with ground glass opacity,
but a greater than five millimeter solid center.

This would be dictated as likely
lepidic predominant adenocarcinoma.

Okay? That's where the terminology has gone.

Fleischner Society Recommendations for Solid Nodules

Now, here is a high risk patient.

He came in for his CT scan
with a pack of smokes in his pocket.

This is one of our clinical scans.

This is one that came through to be read one day.

And if you look at it, if you count those,
there are 19 cigarettes in that box.

So he had a smoke on the way to his CT scan.

Now, even though he is high risk,
that four millimeter nodule
or three millimeter nodule only needs
to be followed at one year
because of the Fleischner Society recommendations.

And I suspect you are all familiar with these.

These were published in 2005
and I think it's been the most downloaded article ever
published in radiology
because it allows us to follow patients
with a reasonable schedule.

That's not every three months.

And in this patient who is a high risk patient
with a four millimeter
or less nodule CT at 12 months is all you need to do.

And then nothing more.

Natural History and Growth Rates of Nodules

Now here's a nice example also of just like in the last talk of the natural history
of a growing cancer,
and this is what you can expect to see with a cancer.

This little teeny nodule grows over time
and that indeed is
what you would expect from a solid nodule, a growth rate
like that where it goes from something small to something
that's bigger in a year or so.

And here's another example.

This one, an interesting case
that also points out another pitfall patient being followed
for that little nodule in the right upper lobe at five
months and 17 months.

And the scan was interpreted as showing no change.

And this is a scan at 28 months.

Also no change, but it was noticed
that there was a nodule there.

And you can go back and see that same nodule
on the other scans as well.

And this is an example of sort of satisfaction of search
where you're looking for a nodule, you see it,
it looks the same and you don't look for anything else.

And also airways are sort of a blind spot sometimes
and it's hard to see nodules in relation to airways.

But again, an example of how a solid tumor
grows at a reasonably rapid rate.

Now, lung cancers actually have a very wide
range of doubling times.

In one study that was reported,
the volume doubling time was from 42 days
to almost 1500 days.

And what I have done in this diagram showing a 12 year
time span along the bottom is for a 42 day
doubling time nodule, this is what it does.

And these are actual size and diameter in about a year.

The other end of that scale looks like that
and this nodule being that big after what, five years
or four years or something of that sort.

So there's a very wide range
of doubling times for lung cancers.

And it turns out that the doubling time is related
to the nodule attenuation.

Ground glass opacity nodules in one study doubling time over
800 days, mixed ground glass
and solid 457 solid nodules 150.

And that makes sense because the ground glass opacity
nodules have a better five year survival
and are much more treatable.

And these represent those adenocarcinomas in situ are
minimally invasive adenocarcinomas.

Now here is a patient with a ground glass opacity,
solitary nodule, probably a couple centimeters
or so in diameter.

It was followed six months later and looks exactly the same.

Is that a good thing or a bad thing?

Well, in fact, it's a bad thing.

Usually we think that if something doesn't change,
it's that's a good thing.

But ground glass lesions either go away quickly
because they're inflammatory
or something of that sort or they're cancers.

There aren't very many other things
that produce this sort of appearance.

And if you have a persistent ground glass opacity nodule
that suggested it's a neoplasm.

And one study that was reported nodules that persisted
of ground glass opacity on CT during follow-up, 75% were
BAC or mixed subtype.

I put BAC in quotes
because that was the terminology used in the article.

It was before that other article was published.

19 percent or so were inflammatory or scar
and 6% something called atypical adenomatous hyperplasia.

I'll mention in a second, this was an
adenocarcinoma in situ.

Now here is our growth rate diagram.

If we take this slowly growing nodule
and I show you what that looks like at two years,
That's what it looks like now, usually two years is
how long we follow a nodule.

And if it doesn't look any
different, we sort of forget about it.

But with these slowly growing cancers, it's very hard
to perceive that change in size in a period of two years.

And particularly if the nodule is a ground glass opacity,
it's hard to see the edge
and make a precise measurement.

So it's been considered
that ground glass opacity nodules need to be followed
for longer than the two years we usually use
for the Fleischner Society recommendations.

Here's a patient with a little ground glass opacity nodule.

He is being followed, he's being followed,
sort of looks the same sort of looks the same sort
of looks the same, sort of looks the same, same.

But if you compare the first to the last,
more than three years later,
it's very slowly increasing in size.

Very important when you're following a nodule
and particularly a ground glass opacity nodule like this.

Not only to look at the most recent prior,
but pull out a prior from a couple years before
and see if there's anything changing over the longer period of time.

Now here's a case that I was a case I read,
I read this probably 15 years ago
and I mentioned this ground glass opacity nodule
and didn't really say too much about it.

I said it was non-specific and didn't recommend follow up
or anything in particular.

This is 11 years later when he came back
and this was biopsied at that point
and was a adenocarcinoma with lepidic growth.

So it's one of those cell types of adenocarcinoma
with lepidic growth, very slow growth here over 11 years.

But this is what can happen
to those if you don't follow them and let them go.

This guy's still doing fine.

Actually he is in his upper eighties.

Follow-Up Intervals for Ground Glass Opacity Nodules

Ground glass opacity nodule.

Which, when should we follow this?

What is the interval we should use
to obtain our first follow up scan?

That certainly is concerning
for a adenocarcinoma in situ.

Should we follow it a year like the Fleischner Society would
recommend for something like that
or six months or three months?

When should we follow up? Well, the rule now is
that if you have a ground glass opacity nodule like this,
your first follow up should be in about three months.

And the reason is that indeed, some
of these are simply inflammatory or infections
or something of that sort, and they'll go away quickly.

And if they go away quickly,
then the patient's not a patient anymore.

It doesn't have to be followed anymore.

He doesn't have to worry about
it, doesn't have to see his doctor.

So the consideration is that
for a ground glass opacity nodule like this
that you pick up, the first follow-up scan should be
at three months.

Now the Fleischner Society recommendations that are
so important and everybody has a hanging on their reading
room walls, have now become the Fleischner Society
recommendations for solid nodules.

This protocol is
what you should use if you're looking at a nodule that is
of homogeneous soft tissue attenuation should not be used
with ground glass opacity nodules.

Now the Fleischner Society just published recommendations
for follow up of ground glass opacity nodules
or pure ground glass opacity nodules.

These were published in radiology earlier this year,
and I will read through these.

They're a little more complicated than the earlier recommendations,
but something that we should be starting to use
and we are using these now in our hospital.

So if you have a solitary pure ground glass opacity nodule
five millimeters or less in diameter, no follow up required.

I'll show you why in a moment.

If the pure ground glass nodule is more than five
millimeters in diameter, initial follow up at three months
to confirm persistence
and then annual surveillance for a minimum of three years.

And what I expect is that three years from now,
these will be reassessed
and it will be determined that the follow up now has
to be longer than three years,
but at least for the next three years
follow up should be for three years.

And then if you have a solitary nodule that's part solid,
some ground glass, some solid initial follow up at three
months to confirm persistence.

If persistent and solid component is less than five
and you basically do the same thing
as if it's a pure ground glass
nodule, follow up for three years.

If it's persistent and the solid component is more than five
millimeters, you need to be very aggressive biopsy
or surgical resection
because that finding ground glass
with a solid center more than five
is highly predictive of cancer.

So a lot of times these will just be whacked out
when you see that finding.

And a couple other things, a few other comments about these.

If you're going to decide
that a small nodule is ground glass, you need
to use thin sections that confirm
that the nodule really is ground glass
and not simply volume averaging.

Pet is of limited value.

Consider pet for nodules if they're over
a centimeter in size
and have some solid component within them.

Examples of Ground Glass Opacity Nodules

A few examples. Now here,
a ground glass opacity nodule five millimeters
or less than diameter, no follow up required.

These are often atypical adenomatous hyperplasia.

I'll describe that in just a second.

It could be a small adenocarcinoma in situ,
I suppose there's nothing to say it isn't, but if it's small
and an adenocarcinoma in situ,
it's gonna be growing very slowly.

At this point, no follow up of these is recommended.

Now, atypical adenomatous hyperplasia is a benign variant
or pre-malignant variant
of adenocarcinoma characterized by lepidic growth.

So it looks a lot like adenocarcinoma in situ,
but it doesn't have a malignant appearance,
doesn't have all the malignant genes
that adenocarcinoma in situ does.

But the mutations are quite similar
to adenocarcinoma in situ.

These are usually five millimeters or less in size.

And the assumption is going to be
that if you see a ground glass nodule five millimeters
or less, it is one of these atypical adenomatous hyperplasias
and you can forget about it, see it as ground glass on CT.

Okay, here's a patient with a scan
and a nodule in the left upper lobe.

You can see it quite nicely
with the arrow pointing at it follow up.

Should we follow this or blow it off? It's less than five.

Well notice this is not a thin CT,
this is a reasonably thick scan.

We can see too much of these vessels for this to be a
scan with one millimeter collimation
or one millimeter slice thickness.

And actually if you do obtain a thin slice
through this lesion, you can see that it's not ground glass,
but is solid, may actually be calcified,
but it's certainly a solid nodule.

So if you're going to say that you have a little nodule
that's of ground glass opacity, you need to base
that on using thin slices.

Six millimeter ground glass opacity nodule
for your follow up looks exactly the same.

At this point in time, we would stop following this,
but those recommendations may change later.

Okay, here is a patient with a nodule on the left upper lobe.

This is a one year follow up.

Lemme see how those appear on the screen. Okay.

What's your impression
comparing the first to the second?

Would you dictate this as no change
or progression of this lesion?

Starts off as a ground glass opacity nodule
with a little bit of solid, and then you see the second scan
progression.

Progression is correct. If you notice the two images,
the first image is the first image shows the
nodule to be principally of ground glass opacity.

A little bit of solid on the second scan.

The nodule is the same size.

The size has not changed, but there's more soft tissue.

Now within it, the soft tissue component is larger.

That is progression for a ground glass opacity nodule.

It's not just simply increase in size anymore,
it's increase in attenuation because that predicts invasion
and this needs to be whacked out.

And here's the two pictures again.

And this is a third study
that shows this is now an invasive adenocarcinoma.

Okay? Now here's a patient that has multiple of these sort
of ground glassy things,
and there are even more around than I've put arrows on,
but you can see each one of these
and each one would be consistent
with adenocarcinoma in situ
or minimally invasive
adenocarcinoma, something of that sort.

And it's important to recognize
that multiple adenocarcinomas like this are common.

This is a person who had already had an adeno resected on
the right side, and this is her left lung with
multiple adenocarcinomas within it.

These all may be relatively slow growing.

You could not go in and whack all these out
or she wouldn't have any lung left.

So you sort of have to follow these and see what's going on.

And if one starts to look aggressive, take it out.

But keep in mind that these may be multiple
and to look for more than one if you happen
to see a lesion that looks like an adenocarcinoma.

Fleischner Society Recommendations for Multiple Ground Glass Nodules

Now, the Fleischner Society has also come out with recommendations for following multiple nodules
that are ground glass or pure ground glass.

And basically if you see multiple nodules
that are either pure ground glass
and small, follow it two and four years.

I'm not sure exactly where those numbers come from,
but that's the recommendation at this point.

Multiple ground glass nodules less than
five, follow it, two and four.

Pure ground glass opacity nodules more than five
without a dominant lesion.

Initial follow up at three months to confirm presence
and then annual surveillance for a minimum of three years.

I can't remember these to tell you the truth.

And this is something that I am gonna have to print
and hang on the wall because it's a lot more complicated than the earlier ones.

And if you see a dominant nodule with part solid
or solid component, initial follow up at three months.

And if persistent biopsy
or surgical resection is recommended, especially for lesions
with greater than five millimeters of a solid component,
that's a very it's a finding very predictive
of lung cancer.

But keep in mind that there are these new recommendations
for ground glass opacity nodules that you should have available,
even though you may not remember what they are.

And I'm a member of the Fleischner Society
and I still can't remember 'em.

And then a few other comments.

Consider alternate causes.

If you have multiple ground glass opacity nodules,
something like hypersensitivity pneumonitis
or some sort of diffuse lung disease.

FDG pet again not recommended
for ground glass opacity nodules
that are mostly ground glass
and consider lung sparing surgery for patients
with a dominant lesion suspicious for lung cancer
and other ground glass lesions.

So in any case, these are available in the literature,
they're available from radiology,
and I wish you good luck in applying them.

And again, here is our case for this annual follow up
for a minimum of three years is what would be chosen.

Diffuse Bronchioloalveolar Carcinoma (Now Invasive Mucinous Adenocarcinoma)

Okay, there was something else we used to talk about.

Diffuse BAC or multicentric BAC
or multifocal BAC where you see tumor involving
multiple lobes, often somewhat nodular,
central lobular nodules are present
and can be solid consolidation or ground glass opacity.

Here, a nice example of central lobular nodules.

This name has also been changed.

It is no longer diffuse BAC, it is now invasive
mucinous adenocarcinoma
because these tumors are almost always the
mucinous cell type.

The adenocarcinomas presenting as lung nodules are usually the non mucinous cell type,
but the mucinous ones are the ones that do this bad thing.

Now, the histology
with these mucinous adenocarcinomas causing all this
consolidation is sort of the same and sort of different.

You have lepidic growth
with tumor cells growing along alveolar walls,
and then the tumor cells secrete a large amount of mucin or
or fluids, serous fluids sometimes, but mucin.

And it's the mucin that consolidates the lung
that fills the alveoli
and gives these large areas of consolidation.

So these are not all tumor.

These abnormalities represent a combination
of lepidic tumor growth, some invasion, and then lots
and lots of mucin secretion.

And here another example of a invasive mucinous adenocarcinoma with multiple nodules
and ground glass in areas of consolidation.

Other Pitfalls and Mistakes in Nodule Interpretation

Okay, now we'll get away a little bit from ground glass nodules
and talk about some other of my mistakes.

Here a patient I saw in 1997,
this patient was having CT
because he had an aspergillus infection in his upper lobe
and was being followed for that
and was being treated for it.

And on a CT he had this funny little cystic thing at the
right base with a little nodule in association with it.

But nobody thought too much of it
because his upper lobes were much more abnormal.

Six months later, again, he's being followed
for his aspergillus and he now has this large nodule
or mass in that same region.

We didn't know what it was.

We thought it could be part of his infection,
but we were certainly worried about cancer.

So a biopsy was scheduled.

He came in for his biopsy
and this was the CT that was done at the time of his biopsy.

Before I passed the needle, I was getting things localized
and all that, and the lesion was clearly smaller.

Well being the genius I am, I canceled the biopsy
and he continued to be followed for his aspergillus.

And then here is what it looked like later.

And at that point it was biopsied and was carcinoma.

And the important point to take away from this case,
and I've made this a number of times, is
that a single follow-up CT showing decrease in nodule size
is not sufficient for calling it benign.

And I know of malpractice cases
that have turned on this point
where a nodule was decreasing a single decrease in size on a CT scan nodule was called benign
and then turned out to be a cancer later on.

Cancers can transiently decrease in size
and don't make this mistake, keep following the lesion
until it goes away or continues to get smaller.

Single follow-up study is not sufficient.

Now these are things we see all the time,
these little sort of triangular things
that the pleural surface, the residents love
to call these nodules.

And some of my clinical, some
of my faculty colleagues call these nodules as well.

But if these are triangular in shape,
and particularly if the edges are a little bit concave,
I just ignore these, I'm not sure what they are.

They may be little subpleural lymphoid aggregates
or they may be little scars or old infarcts or something.

I just don't know and really don't care
because they're never significant.

So these, even in a cancer patient,
I always blow off when they have this appearance.

Now there have been a couple articles published in
the journals and radiology about nodules
that are adjacent to fissures because these are also things we see all the time.

And here are some examples of these per fissural nodules
that invariably are nothing.

And this one has that same shape I just showed you.

It's triangular. It has sort of concave edges.

Again, I'm not entirely sure
what these are all the time,
but they are not of significance.

And here's one that's sort of pancake like along the fissure that also is an appearance
that predicts nothingness.

And here's some diagrams from the paper
that was published in these typical per fissural nodules
that have this sort of pancake shape or oriented along the fissure
and have a good deal of contact
with the fissure itself, always benign.

Whereas these nodules that have a rounded shape
and less contact with the fissure are of more concern.

Now in this study, they looked at 3000 heavy smokers
who were screened with CT for lung cancer.

23%
of more than 4,000 nodules they detected were per fissural.

Some of them grew up to 23% of these nodules grew,
but none had a rapid doubling time and none were malignant
after 5.5 year follow up.

So these little things you see along the fissures,
particularly when they have this shape are something
that you'd need not be concerned about.

This is a case we saw a patient with a colon cancer
and he has a subpleural nodule.

It's not per fissural, but it's certainly subpleural.

And this is a shape that you cannot call one
of those benign per pleural nodules because it's rounded
and the diameter of the nodule itself is
a little greater than the amount
of contact it has with the pleural surface.

This is an appearance that's not necessarily benign
and this was resected,
but it was an intrapulmonary lymph node, a benign lesion.

But this is not an appearance that you can let go.

Okay? This is a case I saw at the
San Francisco General Hospital not too long ago,
and actually it's a case I got right?

So I'm showing it because of that.

A patient who came in,
I can't remember why he came in cough or something like that
and had a chest film that was abnormal.

And this was his CT scan.

And the simple question is here, benign or malignant.

Now at the county we see lots of TB
and I think a lot of people were thinking this was going
to be TB or something of that sort.

But this appearance is actually highly
predictive of carcinoma.

And I'm not sure exactly how to describe it to you,
but it's sort of a bubbly appearance.

It's not cavitary per se,
but more bubbly with these little thin septations.

And it's an appearance that is not uncommon
with adenocarcinoma, sometimes adenocarcinomas
with lepidic growth, but it is certainly an appearance
that suggests cancer.

And because of that, he was biopsied right away
and it was an adenocarcinoma.

Air-Containing Nodules

Now, air containing nodules is what I'm going
to talk about now, and
that certainly was an air containing nodule, something
that is cavitary contained cystic spaces or air bronchograms.

And in one study, 23 of 42 cancers
or two thirds contained air.

So air within a cancer is pretty common
and it's much less common with benign nodules.

So if you see a nodule with cysts in it or cavities
or air bronchograms, keep in mind that these
are likely cancers.

And think about cancer when you're giving your
differential diagnosis.

In this one study, and again, this is from a study that was
on patients being screened for lung cancer, 62%
of air containing nodules were malignant.

There it is again, a cystic adenocarcinoma.

It's not cavitary but cystic. And here's another one.

This one I didn't get right and
because of this one, I got that second one correct.

But this is a patient who presented
with this funny thing down here
and this just looks like some atelectasis to me.

And then it has this funny cystic appearance to it.

It doesn't look cavitary, but it looks cystic
and there are bronchograms in it.

And I said, I don't know what this is,
but it's probably a pneumonia
or some old scarring from a pneumonia,
but another adenocarcinoma.

So if you see these cystic things, keep in mind
that these can be cancers.

This an appearance
of an invasive adenocarcinoma with air bronchograms.

It's something we see all the time.

I don't think anybody would say, this is not a cancer.

All lobulated speculated looks very dangerous. Okay?

Cavitary Lesions and Wall Thickness

Now, something I teach the residents is that you can
determine what a nodule likely is
or what a cavitary lesion likely is
by the thickness of its wall.

If a lesion has a wall
that is less than five millimeters thick,
the large majority are benign.

Large majority. If you have a lesion
that has a thick and nodular wall
and the thickest part of the wall is more than 15
millimeters, that's very likely malignant.

This is what I teach them.

And from constantly teaching them this over time,
I actually come to believe it,
which is not necessarily a good thing
because as soon as I trot this out
and try to use it in a clinical case to say something
with any degree of certainty, I'm usually wrong.

But keep in mind
that benign lesions usually have a relatively thin wall.

Malignant lesions usually have a thick and nodular wall.

But make sure that you mentioned both benign
and malignant when you're describing either one
of these appearances because they can be the opposite of
what you think that was coy a cancer.

Okay, two additional cases.

Same sort of criteria on your left smooth wall,
less than five millimeters.

I mean, that's like two millimeters thick on your right,
that gnarly looking wall that's a met
and that's TB of course.

But so the exact same appearances can be seen in
either of those things.

And even though statistically those statements are true,
they don't always work.

And again, whenever I try to show off
and say, I know exactly what this is, you know,
that's the time I'm going to be wrong.

Another example of a thin walled smooth walled cancer here,
a squamous cell with growth over three months,
and it starts off as a thin walled cyst
and turns into a bigger thin walled cyst.

Now another rule I have that I teach the residents,
if you have a cavity with an air fluid level
that very likely represents a bacterial lung abscess,
other causes of cavities are not typically associated
with air fluid levels.

Cancers don't usually have fluid in them.

TB usually doesn't.

It's just sort of a nasty looking cavity,
but not with the fluid level fungal infections.

Fluid level's pretty uncommon.

But again, you can't hang your hat on this finding,
even though these are statistically valid statements.

Here are a few more examples. Nice air fluid levels.

These are all cancers. Now what's going on here?

I don't know. It could be infection of a cancer.

Cancers can become super infected. Cancers can bleed.

This could be blood in a cancer.

But these are not always abscesses a patient with a very thin walled cyst in the left lower
lobe, but looks a little bit like an ice cream cone.

But this I think we've been following for a while.

I'm not sure why this patient was having continued CT scans,
but we were seeing this little thing for
quite a number of years.

And then all of a sudden on a follow up, it looked like that

This is a cancer originating in cyst.

There is a higher incidence of cancers in
or an increased incidence of cancer in association
with cysts or longstanding cavities probably
because of fibrosis.

But these benign cysts
or whatever they are, can turn into cancers over time.

Lung cancer associated with the cyst
or bulla, they can arise in areas of scarring
and in relation to preexisting cyst cavities
or bullae, thickening of the cyst wall filling in of a cyst
or accumulation of fluid are
findings that you should worry about.

Air Crescent Sign

Okay, this is a classic appearance.

This is a patient with an air crescent sign, a crescent
of air capping a rounded opacity.

And this of course is a finding that's very typical
of mycetoma or aspergilloma.

And here on a prone scan you can see that
that flops forward.

So it's mobile within the cavity.

Again, very typical of a mycetoma.

And anytime I show an air crescent sign, the residents say,
well, this looks like a mycetoma.

And I say, what's the differential diagnosis?

And there's silence in the room.

But there is a differential diagnosis for air crescent sign

Mycetoma Angio invasive aspergillus does something
that looks very much the same.

Necrotizing pneumonia can do it,
just it's sometimes called pulmonary gangrene,
but you get a necrotizing pneumonia
and a little ball of dead lung drops off into a cavity.

Cavitary cancer or cancer arising in cyst, the kind
of cavus I've never seen that

Blood clot GLO cavity papillomatosis a Rasmussen
and aneurysm, which is a pulmonary artery aneurysm occurring
in a TB cavity.

But this the differential for air crescent sign.

And keep in mind that malignancy is on the list.

This is a very nice example
of Air Crescent sign in a patient with angio invasive aspergillosis, a patient
with leukemia on chemotherapy
and with angio invasive aspergillosis,
you get a septic infarction
and the ball of lung
that has been infarcted drops off into the space it used
to occupy and gives this typical appearance
of an air crescent sign.

And this is what it would look like
or what it does look like on path.

You get this ball of dead infarcted lung inside a cavity.

This the same sort of appearance in a patient
with necrotizing staph pneumonia with pulmonary gangrene,
a mass in a cavity representing dead lung.

And here are two cases, a nice air crescent sign here, here, sort of a donut variant
of an air crescent sign.

These are both cancers, lung cancer
with an air crescent sign, sort of funny looking cavitation
and same sort of thing here in a metastasis, sort
of a little infarcted
or dead part of the tumor within the area of cavitation.

Halo Sign

Now this is a patient with leukemia
and a low white cell count.

And this is an example of the halo sign where you see a halo
of ground glass opacity.

I can barely see it here surrounding a dense
nodule halo sign is very typical of
angio invasive aspergillosis in patients with leukemia
and low white cell counts.

And indeed that's what this is,
angio invasive aspergillosis.

And this is what that looks like.

This is the septic infarct, it's surrounded by hemorrhage,
and it's the hemorrhage that causes the halo.

And then as this progresses, this part
of the dead lung drops off into the
cavity and you get a crescent sign.

But this is how it starts off
septic infarction in the middle, surrounded
by a halo of hemorrhage.

Now the halo sign also has a differential diagnosis,
and I'm not gonna run through all of these,
but it's a long differential.

And down at the bottom I'd like to point out
that adenocarcinoma does this.

I have shown you several examples of adenocarcinomas
with a dense center
and ground glass around it,
a lepidic predominant adenocarcinoma
or a minimally invasive adenocarcinoma.

So keep that in mind when you see Halo sign.

And here is a case I showed you earlier
and here, a pulmonary embolus with infarction
that showing a halo sign.

Final Case: Missed Foreign Body

And this I will finish with this case since we're talking about air within a nodule,
this is a case I certainly missed
and I think I will miss this case every time I see it.

This is a patient who was seen in the emergency room at
San Francisco General.

I didn't know that at the time.

It was a number of years ago.

And he was seen there for a stab wound
and was bleeding rather profusely.

And his wound was packed with a bunch of four
by fours and somehow he was then discharged.

And what we're seeing here is a space
or hole in his lung filled with four by fours that were left there.

Okay. Thank you very much.