Thoracic Lesions: Part 1 (Parenchymal Nodules)

Introduction

Good afternoon.

I'd like to thank Mike Fa for inviting me.

It's a pleasure to be here and an honor to be amongst such distinguished faculty.

As you can see, my subtitle for the talk is from Nodal to Nipple.

Nodal will be today, and almost all the rest will be tomorrow.

Please come tomorrow.

Incidental Findings

Again, incidental finding, any finding that is either unsuspected or unrelated to the clinical indication for imaging.

And since sometimes we have a very specific indication like a PE or a coronary scoring study, anything else ends up being incidental.

No doubt why we have so many incidental findings.

However, incidental definitely doesn't equal insignificant.

And when we encounter those incidental findings, we should categorize them into those that require immediate action, such as a newly discovered malignancy, or of course a PE.

Those findings that are recognized should be reassessed eventually, but there is no rush, no urgency, and those that we should recognize and just be aware of, name them correctly, and no recommendation for any additional workup, even in that case, like a very vascular anomaly might be sometimes important in the future.

Like a patient who has maybe double superior vena cava and gets a central venous line, and it ends up being on the wrong side.

And then if we have that information, it's very useful and might prevent additional concern.

Case Study: Multiple Incidental Findings

This is sort of a typical CT chest study that I encounter almost every other day, an 80 or 84-year-old female.

All it says on the requisition is follow-up study.

And somebody asked about the thyroid, so I won't mention it very much, but you can see that she's got this large thyroid mass.

And scrolling down, she's got a lung mass scrolling down, she's got a anterior mediastinal mass.

And as I keep going down same study, she's got a chest wall mass.

And just a little bit further down, she's got, at least this is straightforward.

It's a fatty liver and bilateral adrenal masses.

And all this is before I looked at the lung window or the bone window.

So fortunately, the PACS was working well that morning, and I was happy because, oh, she also has diverticulosis and she has a study from 2007, which is her first study at Stanford.

And it says then she was much younger, 79-year-old with chronic bronchitis and cough.

So at least we know why she gets that study.

And it's a non-con study.

You can still appreciate the thyroid mass was there, the lung nodule smaller, but was there four years?

It's 2007, 2011, the anterior mediastinal mass.

Was there additional findings that are more obvious?

Here are the lipoma to hypertrophy of the inter atrial septum going down the world.

The skin or subcutaneous nodule is there smaller, she's gotten a hiatal hernia that's more obvious on that study, this fatty liver and bilateral adrenal masses.

So I was sort of very pleased with that lady because I was like in my imagination, I was quite sure that somebody must have offered her to look into these.

And she was confident enough to say no, thank you.

But then to my great surprise, I noticed that just two months later when I was preparing this talk, I realized she underwent surgery for all of these and the right upper lung.

So now she's 84 and she has, it turns out she has a carcinoid in her right upper lung.

She has a thymoma and she has a thyroid carcinoma.

Exactly.

So it makes you wonder, do we really help them?

Do they need all this input?

Why would she go undergo this makeover at 84 that would probably be associated with much more morbidity than the mortality that those tumors have shown us to be rather slow growing.

And this is unfortunately not too rare.

Significance of Incidental Findings

So significant incidental findings, depending on the studies that one looks at range from 3%, I don't think many of them only have 3%.

Many of them have even more than 41%.

And I think the main concern is that there isn't any uniformity regarding what those clinically signify and what the recommendations should be.

So one such study, and there are many more out there, is a study looking at about nearly 600 cases.

Studies that were done for PE in the emergency department while PE study PE positive were less than 10% incidental findings that were deemed important or significant were more than double than that.

And the most frequent one were not surprisingly lung nodules and mediastinal lymphadenopathy.

And then concluded quite rightly that if you get a CTA for a PE in the ED, you are very likely to encounter incidental findings that will probably be require more imaging or other interventions.

Topics Covered

So after this introduction, these are the topics I'm going to try and cover, however, this afternoon will be nodules, nodules and more nodules.

And these are the categories.

I'm going to discuss solid nodules, ground glass nodules, and a few words about pleural nodules and subpulmonic lymph nodes.

The Incidental Lung Nodule

Definition and Characteristics

So the incidental lung nodule, it's probably not a right name because I usually nickname it in my for myself as the inevitable lung nodule.

And in the era of chest x-rays, we would call them the solitary pulmonary nodule, because if we were lucky, we would see one nodule and we would try to characterize it, maybe it's calcified and so on and so forth.

In the era of MDCT, one doesn't really see any more single nodule.

It's very rare.

If you see one, just search a little better, you'll find many more, especially if you scroll through one millimeter scans and with the help of MIP, which I will mention later on.

So just to be sure that we are all on the same page.

So the lung nodule, what's the definition?

It's a rounded or irregular opacity that measures up to three centimeters in diameter.

So quite big.

It can be solid or nonsolid, which are also referred to as the ground glass nodules.

And they must be separate from the pleural or vascular surface of the lung completely surrounded by lung parenchyma.

So this is unfortunate that most of these nodules are of uncertain significance and many require further evaluation.

I guess that's why we are here.

And of course, they increase the workload and result in multiple clinical appointments, anxiety for patients financial burden.

And if those nodules are resected, the cost is quite substantial.

Frequency in the epidemiology, almost some studies show that about 50% of patients above the age of 50 have lung nodules.

So they're extremely frequent, multiple and almost always not solitary.

As I've mentioned, most nodules are less than one centimeter, and most of these small ones are even smaller than five millimeters.

Data from cardiac CT studies show that smoking is not necessarily associated, though other studies would show probably a bit different information.

Benign Features and Management

So what's the first step that we should do when we have encountered this unsuspected or inevitable lung nodule is look for characteristic features that are reassuring for benignity.

These will separate those patients from the other ones that might need additional follow up.

So the features that are associated with benign nodules, first of all, calcification, then internal fat.

So these two would either indicate granulomatous disease in the past or a hematoma, their shape if they're polygonal and not rounded.

If they're ovoid, again, it could be coffee bean shaped flat or tubular.

And if they're clustering of sub centimeter nodules in one lung segment, lower specificity is associated with if they're solid and have no ground glass components.

These are less specific for benignity, if they're subpleural or have punctate calcification, however, we can look at them endlessly and really ponder.

However, careful assessment of the morphology usually does not really enable us definite differentiation between benign and malignant nodules.

Often we are taught or we believe that spiculate or ululate contours would direct us towards the malignant nodule.

However, you can see that's there is a huge range of how certain that is.

And over 50% of smooth nodules are malignant.

So the presence or absence of speculation is really of little help the presence of nonsolid.

So ground glass components usually increases the likelihood of malignancy.

So before we even decide is this a lung nodule, we should be quite sure about that.

And you'll see how this lung nodule looks in five millimeter slice a little bit more distinct on the one millimeter slice, and often worthwhile looking at the coronal reformats and widening the window.

And we can see that this is a small lipoma, so not important, and we shouldn't call it a lung nodule.

It's also not surrounded by lung parenchyma, we have defined, and another one so often when they are very low adjacent to the diaphragm.

Look at the coronals or the sagittals in this case.

And this is, again, a little bit of fat herniating through a Bochdalek hernia.

What about this one?

This is definitely looks like a lung nodule.

And scrolling through the data set, you can see that these, there are two vessels here, and so clear cut AV malformation and not a lung nodule.

And again, better seen on the coronal.

So you can see the so-called lung nodule and the artery in the vein going back and forth from this.

So an AV malformation in a patient with hereditary hemorrhagic telangiectasia.

Size, Growth, and Malignancy Risk

So we are mainly concerned with those lung nodules that will turn out to be lung cancer.

And really, very few of the very small ones will turn out to be malignant.

So nodule size is of course associated with the likelihood of malignancy.

And when we talk about the nodules that are above two millimeters, they have a large likelihood of turning out to be malignant.

But for those that are in the range of below one centimeter, especially eight millimeters sort of a cutoff, it's a much lower likelihood, but still not negligible.

We all know that solid lesions that prove to be lung cancer tend to grow rapidly, and the volume doubling time of malignant nodule is about 200 days.

So about what, eight months or so?

Seven, eight months.

Whereas when we follow a nodule and we see that it's a volume doubling time is about a year and a half, the majority of them, again, not all of them will turn out to be non-malignant.

However, there are some exceptions.

And therefore, there are some recommendations we'll touch to that a bit later.

Indicate that measurement follow up should be at least three years or up to three years and not two years.

This 77-year-old male had no lung nodule here.

He was in a follow-up for other lung nodules.

And on the 2009, this nodule is the first time that it's recognized, maybe retrospectively, you can see that there is a tiny little here as well.

So 2009, there is a new, that wasn't even the one, the reason for follow up.

And you can see that a year later it's really doubled quite significantly, at least doubled the size.

Don't forget its volume.

And this turned out to be a neuroendocrine cancer.

Fleischner Society Guidelines

So the guidelines, the ones that as mentioned before, we follow and are indeed posted everywhere, and we all sort of pray from them, those of the Fleischner society.

And they look at the first of all, the risk of the patient in their guidelines.

Actually, they talk about the high risk regarding age, they talk about 35.

So I found this other paper because I thought 35 was sort of insulting for old age for, and this is a different reference that I found.

So the for age wise, above 60 and below 35, 45 is low and high smoking is of course, a major risk factor.

And previous malignancy in the recent years also is a high risk factor.

So these are all in the syllabus and below four millimeter.

If the patient is a high risk, he does need, even though it's such a tiny nodule, there is indication to follow up one more time.

Above eight millimeter, we mentioned the eight millimeter as being the cutoff.

And in this case, high and low risk.

They get a very constant and many follow ups at very short intervals of several months.

I just want to mention that even though we use this one, and this is probably a very good one, there are other guidelines as well.

And with this is again, a field that is rapidly evolving, might change in the future, and the management decisions should not be based only on the nodule size, even though that's the main criteria, as you've seen.

And I've mentioned other criteria such as clustering of multiple nodules in a single location in the lung.

And even though this often will favor an infectious process, there might always be this one dominant nodule with tiny satellites around it.

So again, we always, there is always this, but it can also be the other one.

Similarly, a location.

So upper lung location is more frequent for malignancy, however, almost every second patient will have some, especially again, older patients will have some apical scarring.

So extremely common and again, not so helpful for us.

Ground Glass Nodules

A few words regarding the ground glass nodule.

So what is the ground glass nodule?

In comparison to the solid nodule, it's a hazy opacity that does not obscure either the bronchial structures or the pulmonary vessels on HRCT, and it can be caused by anything that fills the airspace.

So it can be fibrotic edema or neoplastic.

Again, not very specific benign reasons are infection, focal fibrosis, respiratory bronchiolitis as seen in smokers, DIP hemorrhage, most benign conditions resolve spontaneously or after treatment within weeks or months.

So when do we suspect malignancy is when the ground glass nodules also have a malignant part.

And then there is the spectrum of three different types.

The most benign or the most early precancerous cancer would be atypical adenomatous hyperplasia.

And this can shift into adenocarcinoma with predominantly bronchoalveolar cell carcinoma features into the pure adenocarcinoma ground glass nodules have a different growth rate than those that are solid.

As you can see, the solid tend to grow fast, the purely ground glass nodules, and that, again, approaches three years.

So therefore, when we follow up ground glass nodules, two years is not long enough in the Fleischner society.

By the way, the criteria do not specifically mention ground glass nodules.

They mainly focus on the solid nodules.

This 45-year-old male undergoes surveillance because of a prior retroperitoneal liposarcoma.

And you can see this tiny ground glass nodule, it's sub centimeter.

However, in this case, there was no follow up.

It was resected immediately.

It turned out to be atypical adenomatous hyperplasia.

So a few words about that.

It's as you can see, a ground glass nodule.

And it has the spectrum that I've mentioned before, and I really want to stress that PET CT in these cases, unlike the solid nodule, will be negative.

So a false negative that might mislead us if we want to evaluate these prior to either resection or biopsy.

This 63-year-old man has an abnormal chest x-ray undergoes CT, and we can see in 2005 this quite similar to the other patient I've just shown you.

He undergoes follow up.

Two years later, it's 2007.

Now it's completely unchanged and I guess it's easy to shrug and say, why should we keep going?

But we do.

And it's now 2009.

So four years later it's definitely not bigger.

It didn't change much.

You can see his gut.

Meanwhile, he's aged a bit and he's now got a new pacer, and we do follow him one more time till 2011.

So this is six years.

So it's enough that you see one or two cases like that.

And they're not extremely rare, and you understand that even three years is not really quite enough.

On the other hand, the amount of the quantity of patients who have those ground glass nodules is really incredibly large.

And in this case, he undergoes also a PET CT.

And you can see the avidity.

This is three months later, by the way.

So this is late 2011, and this is early 2012.

So you can see it suddenly completely lost the control it was under.

So he undergoes right upper lobectomy.

And as we expect from those hazy ground glass nodules, this is a moderately differentiated adenocarcinoma.

And in this case, PET CT is of course, positive.

And the uptake of above 2.5 is usually considered an indicative of malignancy.

But again, to stress that PET CT only plays a role in the evaluation of noncalcified nodules when they're above 10 millimeter in their size.

And very important to remember this relatively short list of false negative, which includes carcinoids, bronchioalveolar or adenocarcinomas with BAC features and lesions that are smaller than 10 millimeters.

PET CT usually has high sensitivity, specificity and accuracy against solid and larger than 10.

It's used in sub centimeter, sub solid nodules is not recommended.

Pleural Nodules and Subpulmonic Lymph Nodes

A few words regarding the pleural nodules.

These are quite commonly seen and a nice article recently followed patients who did develop lung cancers in consecutive follow-ups.

And none of the lung cancers developed from any of the pleural nodules that they have noticed.

This is below, you have the reference from radiology 2010.

And they concluded that if those pleural nodules are triangular or oval, usually located inferior to the carina, have a septal connection, usually are small, but they can range up to 13 millimeter.

They have a very low potential for malignancy if they are indeed adjacent to the fissures.

Interesting to note that in that study, they found several of those pleural nodules did grow during the years that they followed them up.

But when resected, they did not show any malignancy.

So even if they do grow, they're probably it doesn't indicate maybe they are part of the intrapulmonary lymph nodes, and this is how they look.

And you can see the fissure clearly here and the small nodule, it's not quite round sort of triangular.

Similarly, the intrapulmonary lymph nodes suggestive features include small size subpleural or peripheral.

The shape is classically should be half moon or coffee bean, and they do have a tiny linear connection if they do have that.

And you can see that connection to the pleural surface, like in this case where there is a tiny tag to the pleura, these are typically lymph nodes.

And you can again see that there are sort of coffee bean shaped.

Estimating Cancer Risk

This is a rather good approach to estimate the cancer risk in those small nodules.

First of all.

So sort of summary, as you assess the cancer risk, which is the smoking and the age, the calcification, the diameter, the consistency of the nodule, if it's solid, it's usually a lower risk when than when it's part solid.

The margin I've mentioned, the speculation is usually higher risk, but again, there is no never and no always nodule shape if it's nons spherical is higher location, higher when it's the upper lobes, more so on the right if it's attached to a vessel pleura or fissure, low risk.

And if it's purely intraparenchymal, it's higher risk regarding the density if the density increases over time, there is increased risk for cancer in that nodule.

The doubling time, the faster it doubles, the higher is the risk for cancer.

Use of MIPs

And I'd like to touch on this technical note.

I don't know how many people use MIPs when they evaluate their lung cancers or lung nodules.

Anybody.

MIPs, not too many.

So this if you want to miss lung nodules, don't use MIPs.

However, if you feel that it might be important to see them, I'll show you the difference.

It's really quite impressive.

So this study published in the AJR a few years ago looked at several MIPs, so the reconstruction in five, eight and 11 millimeter for the slab thickness as well as volume rendering.

And they found that the eight millimeter thickness for MIPs is superior to the five 11 or the volume rendering.

And so if anybody wants to volunteer where the nodule is, no, I didn't think so.

This is the nodule, and you can see how easy it is to see it on the MIPs.

And if I go, if I keep going, same patient, you can see those nodules, they really stand out very easily.

So it makes our work very fast.

And unless one is very bored, it's really much better to look through these than to look through the one millimeters.

You can see.

It really is very easy to see them.

Summary of Lung Nodules

So to summarize the lung nodules, they are the most common incidental finding.

Several guidelines exist and one should really be familiar with them, try to follow them and integrate them in the report and maybe this way also educate the referring clinicians.

However, as I mentioned before, it's a rapidly evolving field, and likely recommendations will change with increasing knowledge from ongoing screening trials.

Airways Anomalies

Tracheal Bronchus

And if I have a few more minutes, I'm gonna just touch about the airways quickly.

So one anomaly that is not very frequent, but might be clinically important is the tracheal bronchus.

This is a congenital anomaly, the errant.

So errant bronchus almost always arising from the right tracheal wall above the carina.

The incidence as probably not from CT studies because I've been looking for them and I don't think they are nearly anywhere.

5% of the studies that I see, they're usually diagnosed incidentally, but they might be important, mainly because patients might have chronic pulmonary disease, persistent or recurrent pneumonia.

So while we all learned about the middle lobe pneumonia, that we should look maybe for an aspiration or other lesions that might involve the main, the right middle lobe bronchus.

Remember, if you see recurrent pneumonias in the upper lung on the right, you want to look if there is this additional bronchus, which is right here in that case, if they are symptomatic, they undergo resection along with the part of the lung that they supply.

Tracheal Diverticulum

And the other anomaly I'd like to discuss briefly is the tracheal diverticulum.

And this is a rare, benign entity.

Again, 1% in autopsies, congenital might be congenital or acquired.

The congenital is more seen in males, has a small narrow communication with the trachea and has the whole tracheal anatomy.

They don't really, it doesn't really matter if they're quiet or congenital, it more matters that they become like a little area that might be a reservoir for secretions and cause chronic infections of the lung.

So patients might present with cough, hemoptysis, dyspnea, and repeated episodes of pneumonia or stridor.

And this is a very interesting case that I really, it made me think quite a bit.

This was a young man who has cystic fibrosis and underwent lung transplant.

And this is, these are his new lungs, his transplanted lungs, and he has many repeated studies.

And every other study he has new pneumonias.

And for some reason, I really inspected carefully this area above, I mean, adjacent to his trachea.

And you can see he's got huge tracheal diverticula.

You can see them here one and another one without the air bubbles in them, which are best seen on the one millimeter, could easily be misinterpreted as lymphadenopathy and more interesting.

So I searched and looked at his pre lung transplant studies.

You can see his, the typical changes of his CF lungs before the transplant.

And these diverticula were there.

And I assume that if somebody would have noticed them, they would've been corrected surgically at the time of transplant.

So sort of an important association.

And since the acquired ones are associated with chronic cough and CF patients tend to have chronic cough, I thought I'd find this association very frequently.

I looked at many cases at Stanford as well as at the literature and to my surprise that there is only one case report describing this association.

But I thought it was an interesting finding, and it's again, an incidental finding, but of great relevance in this case.

Differential Diagnosis

And just to mention the differential diagnosis, when you see this little pocket of air and maybe air fluid level, the other diagnostic option would be a Zenker diverticulum, like in this female.

And this is an out pouching of the pharyngeal constrictors.

It's the most common type of the diverticulum in the esophagus.

Often elderly patients has lots of symptoms, so really important to mention that of course, some patients won't even be able to indicate what the problem is because it can lead to weight loss, malnutrition.

So very nonspecific.

So when we go through the CT in a relatively old patient, it's worthwhile looking carefully at that area for Zenker diverticulum.

And I thank you very much for your attention.