The Sonographic Evaluation of Diffuse Thyroid Disease - HD

Introduction

Hi, I am Joe Langer from the Pearlman School of Medicine at the University of Pennsylvania, and my lecture is entitled The Sonographic Evaluation of Diffuse Thyroid Disease.

Today we're gonna talk about diffuse thyroid disease, and basically the division is between Graves' disease and thyroiditis.

The vast majority of thyroiditis is chronic lymphocytic thyroiditis, but there are a number of other types of thyroiditis that we encounter as well.

Sonographic Findings in Thyroiditis and Autoimmune Thyroid Disease

What are the sonographic findings of thyroiditis and autoimmune thyroid disease?

In general, we see gland enlargement. The normal volumes scale by body habitus, but roughly are listed for adults.

One of the things that I find useful is that often the isthmus is enlarged. The normal isthmus is usually about five millimeters, and when it's larger than that, I'm suspecting that there's underlying autoimmune thyroid disease.

But sometimes, in fact, you can have advanced autoimmune thyroid disease and your thyroid is normal in size or even a small gland.

Most of the time we will see some altered parenchymal echo texture or echogenicity alterations.

We may see increased vascularity. For example, Graves' disease has very marked vascularity in the majority of cases.

We may in fact see some reactive lymphadenopathy, but this is usually very minimal and in the central compartment of the neck and anything beyond that should raise some suspicion that there is a secondary process, which we'll talk about as well.

Here's a normal thyroid here on the lower right aspect, and we can see homogeneous sort of bright echoes. The isthmus is about four millimeters in size, and here's a patient with Graves disease. The thyroid is diffusely enlarged. The isthmus is bigger, almost eight millimeters in size. The overall gland echogenicity is hypoechoic, and the echo texture is a little bit more heterogeneous than we typically observe.

Evaluation of an Enlarged but Normal-Looking Thyroid

One situation that commonly arises is the thyroid is enlarged for a patient of that particular size, but it's otherwise completely normal looking normal and echogenicity normal in architecture.

What could this mean? The most common reason is just normal variation. As I mentioned before, if the patients of large height or large BMI, the thyroid just may be enlarged to scale to that particular body mass index thyroids tend to be bigger in women than men. They tend to be bigger in some particular racial preferences, and they tend to get larger with age.

So really what you wanna know about the particular patient is what is their serum thyroglobulin. If the serum thyroglobulin is normal at the time you encounter a large gland, that is most likely a normal variation.

But it is recommended that the patient undergo a serum TSH checking in the future. And we'll talk about that in a moment.

Mild iodine deficiency, in fact, may be a cause, and then you may have transient enlargement of the thyroid, for example, in pregnancy, the thyroid can grow up to one third of its size, and some chronic medical conditions like chronic renal disease will give you a thyroid that's enlarged.

But one thing that has come to attention is that this in fact could be a marker of either subclinical or early autoimmune disease.

So as I mentioned before, you check the serum TSH at that time point, but then need to pay attention to it later.

This was a very interesting article that was published in Slovakia that looked at over a thousand young adolescents. The mean age in this group was 18, excuse me, 17. And they correlated the thyroid volume with the patient's serum TSH and thyroid antibodies in at least 50% of the population. And they assessed whether there was a relationship between an enlarged thyroid and early or subclinical thyroid dysfunction.

And here's what they found of the people that had relatively normal gland size, which was about 81% of the cohort as you would imagine, and those that had only minimal enlargement about 13%. There was a very small likelihood that those patients in fact would have an abnormal TSH or subclinical hypothyroidism. And about 5% of the cohort was antibody positive, meaning they had underlying chronic lymphocytic thyroiditis.

Of those that had an enlarged gland, you could see that 10% had subclinical hypothyroidism and 20% had antibodies.

And so there is some correlation, even glands that look normal in volume or only minimally enlarged a very low incidence of subclinical hypothyroidism. But as the gland becomes enlarged, it's much more of a real concern. And the serum TSH is a very nice way to screen for that.

Graves' Disease

Let's talk first about Graves' disease. Usually it's not a sonographic diagnosis. The patient has very typical laboratory and clinical presentation, but sometimes the patients will come for imaging.

The Graves' disease is a hyperplasia of the follicles, which become very densely packed. They start to lose their islands of colloid, and the gland becomes enlarged, but tends to have a very smooth surface. It has very little fibrosis, and in essence, it's just a very densely cellular hyper functioning gland.

And these findings are mimicked in the sonographic appearance. Here's the patient with Graves disease over here where we can see there's overall hypoechogenicity reflecting the cellular infiltrate in this gland, and it tends to have a more scalloped or lobulated margin. The echo texture can be normal or it can be diffusely or more focally hypoechoic. But this lobular surface contour is a relatively pathognomonic finding.

As we mentioned before, when we do color doppler, it can range from mildly increased to markedly increased something that's been called the thyroid inferno and the blood supply extrinsic to the thyroid. The superior and inferior thyroid arteries will often have very high velocity flow.

And in Europe, some people make the diagnosis of Graves' disease with very high sensitivity and specificity, just using this particular cutoff of 40 centimeters per second in the artery, and do not refer these patients for nuclear medicine testing to make the diagnosis of Graves disease.

As I mentioned before, you can use thyroid sonography to make the diagnosis of Graves disease. It's more common that many people in fact use an I-123 scan.

And this was very interesting data that looked at patients who had I-123 scans and also had sonographic surveillance of the gland. You could see that sonography identified focal nodules in 16% of the Graves patients as compared with nine or 2% found on the I-123 scan. And in fact, in 30 of these patients, nearly half of the patients actually wound up having thyroid cancer. And these were occult on the I-123 scan.

In the vast majority of patients in our particular institutions, all patients with a new diagnosis of Graves' disease undergo sonography just to make sure there's not an occult cancer in that gland. If there is occult cancer, those patients would be managed by surgical removal of the gland, obviously, as opposed to being carried with medical therapy.

Here's such an example. This was a non palpable nodule. As you can see here, it's about 10 millimeters in size with calcification. This was occult on physical examination, occult on nuclear medicine scan, but was a biopsy proven papillary thyroid carcinoma. This patient was treated with surgical removal of the gland treating both the cancer as well as the Graves disease.

Now you will see some patchy regions in patients that have graves disease. And what are these? Both of these were biopsied and they prove just to be lymphocytic infiltrate within the gland. You do have lymphocytic infiltrate within Graves disease, although we tend to think of this as diffuse process. You have to remember that it may be an asymmetric diffuse process. You may have areas of the gland that have more cellular compaction, areas of the gland that do have a little bit of a lymphocytic infiltrate.

What's typically missing in Graves disease is fibrosis. Fibrosis is much more commonly seen in lymphocytic thyroiditis as we'll see in a moment. And so we did biopsy both of these.

Now, unless these hyperechoic areas are relatively large, larger than 15 millimeters, we won't biopsy them because the vast majority of them do prove to be benign on FNA.

Chronic Lymphocytic or Hashimoto's Thyroiditis

Overview and Prevalence

Now we're gonna switch gears to chronic lymphocytic or Hashimoto's thyroiditis, which is far and away the most common type of thyroiditis that you'll see. In fact, it's estimated that five to 10% of the adult population would have areas of thyroiditis in their gland if they were sampled.

It's an autoimmune disease that's much more common in women than men about a ninefold predominance in women and a very strong family predisposition such that if you identify one member of the family that has this disease, there's often several members who have it, some of them previously undiagnosed at the time you're making the diagnosis.

The patient could be euthyroid, hypothyroid, or even transiently hyperthyroid due to cellular destruction and just releasing of T4 into the bloodstream. And about 95% of them will have the circulating antibodies if you test for it.

Microscopic and Sonographic Appearance

My thought of how this looks under the microscope is much like a cobblestone street here in historic Philadelphia, and that is that the fibrosis that runs through this gland makes a cobblestone pattern of the gland, which is something that often gets confused with a multinodular appearance. And we'll talk about how that is quite different.

This gland is not particularly enlarged. You notice there's asymmetric involvement of one lobe as compared to the other. Again, very common that although this is a diffuse disease, that you have a relatively asymmetric involvement of a diffuse process.

So as I mentioned before, there's a lot of variability in how this can look in ultrasound, the gland could be enlarged, it could be normal, it can even be small in size. The parenchymal echogenicity tends to be hypoechoic, but that could be patchy regions or it could be diffuse. And in fact, the ultrasound can have these changes before the patient becomes antibody positive. That's been reported in at least 15% of patients. And something that's a little bit more common in children who may have these areas long before they become abnormal in terms of their laboratory abnormality and the hallmark of this disease, this disease is fibrosis and that's a very important distinguisher between this disease and some of the other types of diffuse thyroid disease. For example, graves disease that I just mentioned before, vascularity is very variable. It can be high or low. High vascularity tends to correlate with active immunologic destruction of the gland and low vascularity periods of quiescence and small lymphadenopathy is very common, but particularly in the central compartment of the neck.

So here's a normal thyroid with a thin isthmus contrasted with a Hashimoto's gland. In this case, the isthmus is enlarged. Look at the overall echogenicity. Relatively bright, relatively dark, and these white lines running through the gland that represents the fibrosis. A very important feature in Hashimoto's thyroiditis. Three millimeters as compared to seven millimeters on the sagittal view, homogeneously increased echogenicity as compared with the paratracheal muscles and very nicely depicted here, very patchy dark echogenicity equal to the strap muscles with these multiple little areas of bright echogenicity. And then these echogenic lines representing fibrosis running through the gland. This gland is almost normal in size. The isthmus just minimally enlarged, again, emphasizing the heterogeneous appearance of these glands and the diverse appearance that we'll see.

Pseudo-Nodules and Patterns

Now, one thing that you might see relatively early in the course of the disease is this particular pattern where we have these sort of geometrically shaped hypoechoic areas, admixed with relatively normal appearing areas of the gland and these so-called pseudo nodules, pseudo nodules, because they're not nodules in the sense that these are a thyroid lesion suspect for thyroid carcinoma. But pseudo nodules in the sense that what these areas represent is lymphocytic infiltrate within the gland. As I mentioned before, they tend to be very angular or geometric in configuration as opposed to round or oval. They're usually seen in conjunction with fibrosis, these white lines running through the gland or a very uneven look to the capsule, both manifestations of fibrosis. And the vascularity can be anything from increased to decreased both within these nodular areas as well as within the gland itself.

Again, here's a micronodular pattern, and I don't call this a multinodular goiter in particular because many of these glands are not enlarged, and a multinodular goiter is usually a gland enlarged by multiple geographically similar areas of nodular goiter or hyperplastic nodules. Instead, I refer to this as a micronodular pseudo nodular appearance where it's really an infiltrative process within the gland as opposed to specific individual nodules. Again, the cobblestone street appearance as compared with scattered nodules within a normal appearing background parenchyma.

Microscopic Correlation

Now if we look under the microscope, in fact, we can see each of the different pathologic processes represented in the sonographic depiction. So here under the microscope, we're gonna see some normal follicles of the thyroid admixed with the changes of chronic lymphocytic thyroiditis. We're gonna see the lymphocytic infiltrate, which even with germinal centers being established within the gland, and we're gonna see some areas of fibrosis when we look at our thyroid gland. The yellow area here will show us some preserved parenchyma, relatively normal appearing thyroid over here, the lymphocytic infiltrate appearing as these hypoechoic areas. And then these bright lines representing areas of fibrosis. So a very asymmetric distribution of a diffuse disease throughout the gland. Just recapitulating what we see under the microscope, what our pathology colleagues have realized for a very long period of time.

If we look at this video clip here, in fact I think this brings this out very nicely. We can see those white echogenic lines very clearly admixed with these hypoechoic areas. We can see the capsule of the thyroid is very irregular, and this is very typical of Hashimoto's thyroiditis. This gland, again, being normal in size, but one of the very prototypical features being these white areas of fibrosis as a hallmark in distinguishing this from some of the other diffuse thyroid processes.

Here's the sagittal view. Again, we can see these hypoechoic patchy areas in this instance nearly entirely replacing the gland. The irregular anterior capsular surface is somewhat lobulated, but irregular posterior surface and the fibrotic fibers running all through the parenchyma of this gland.

Distinguishing Pseudo-Nodules from True Nodules

Now this is something that's very common where an ultrasound will be performed and cursors will be put around these areas and these can be mistaken as nodules. The key here is this white line that you're seeing here on these two transverse images of the left lobe of the thyroid. This white line tells me in fact that this is not a nodule and a nodule, but I'm highly suspect that this white line represents a sort of interstitial space running through there. The white line around these making these look like very focal abnormalities. But if I can look at these abnormalities in the sagittal view, I'll see that that white line was just an interstitial space of the thyroid. And there is no true nodule here nor here. This is just the thyroid parenchyma offset by this white line here in this patient with chronic lymphocytic thyroiditis.

And this particular tongue like extension, some people call this the tubercle of Zuckerkandl. A normal piece of the thyroid here becomes exaggerated as the gland begins to enlarge and look very heterogeneous in the setting of chronic lymphocytic thyroiditis. And so this is not a nodule at all, it's just an irregular area of the thyroid living next to this white line. And if we look behind this was that this tubercle of Zuckerkandl here, just thyroid parenchyma there, the white line is giving you the pseudo appearance of these being nodules. But when we look from another angle, in fact, we can see there are no true nodules within this particular gland.

And I call this the cleft sign. This is just a little cleft, like a splenic cleft running through the thyroid parenchyma at this particular location. I feel as though this is very well seen on real-time examination in this particular individual here. The appearance here of this sort of patchy hypoechoic area on still images could mimic a thyroid nodule, but I could see this cleft just running right on top of that. This is just part of that cobblestone pattern, which is really all throughout the gland. And on a static image, this could simulate a pseudo nodule, but the ability to see the entire gland and appreciate this as a field effect is very helpful.

Now, sometimes I think it is in fact very challenging to distinguish a very sort of infiltrative hypoechoic area here. Is this a nodule that has some features that overlap with papillary thyroid cancer or is it a pseudo nodule in the sagittal view of a different patient? Here I would feel a little bit more comfortable saying that these appear to be a field effect.

Is there anything that we can do to sort of help us out? And sometimes, color doppler in fact can be helpful if the color Doppler shows no mass effect. The vessels just course through here. We know there's not a true underlying lesion having mass effect in displacing these, but in fact, focal thyroiditis is one of the mimics of papillary thyroid carcinoma. Sometimes you may have to biopsy a particular area if you're not sure, but using color doppler, in my opinion, sometimes can be a very helpful discriminator between these overlapping appearances.

Now, here's a gland that was sent to us as a multinodular goiter. This gland is a little bit enlarged, but again, all of these areas here are just patchy areas of the thyroiditis. The white line, again, telling me that this is not a true nodule, this is just an interstitial cleft running through this very abnormal gland. And you can imagine that if you were to palpate this gland, it would feel as a multinodular gland. But instead, when we have a chance to look with ultrasound, we can see that in fact this is that pseudo nodular appearance.

Some glands with very advanced Hashimoto's thyroiditis will become quite large. And in fact, Dr. Hashimoto first described this as patients thought to have multinodular goiters. But when the glands were removed by this particular surgeon, it was just changes of chronic lymphocytic thyroiditis.

At the opposite end of the spectrum, sometimes a Hashimoto's gland will in fact be very small and irregular. This was a relatively large gland in a patient who had longstanding hypothyroidism from the disease.

Association with Papillary Thyroid Carcinoma

Now, there is an association of papillary thyroid carcinoma in patients with Hashimoto thyroiditis. And some of the genetics, in fact has been quite worked out to demonstrate that some of the genes associated with thyroid cancer are more commonly expressed in patients who have Hashimoto's thyroiditis.

Our trick is to try to pick out in the heterogeneous background of a patient with Hashimoto's thyroiditis an underlying papillary thyroid cancer. Sometimes our job is quite easy. Here's a patient with longstanding Hashimoto's thyroiditis. This is the longitudinal view of this particular lobe of the thyroid. And we can see, in fact, there's a very densely calcified nodule in the lower pole having all the features of papillary thyroid carcinoma in terms of dense and coarse calcification here, our job is quite easy that this is clearly a suspicious nodule even in the setting of the hypoechoic background.

And so these are the key things that we would look for. Some of the more typical features that we tend to look for in a normal gland, such as hypoechogenicity, solid consistency and irregular margins, as I mentioned before, can be challenging to detect. They can be occult or they can overlap with the appearance of just spotty heterogeneous involvement of the gland.

Asymmetric involvement is something that you wanna keep your eye on. This can be a key finding, not only for Hashimoto's thyroiditis secondarily affected by lymphoma, which we'll talk about a little bit later, but sometimes can be the presentation of papillary thyroid carcinoma in a Hashimoto's gland.

So here's a film clip of a patient who does have a papillary thyroid carcinoma. You can see the gland is overall hypoechoic, but there is an area that is not only hypoechoic and ill-defined, but has focal calcifications. And so sometimes the nodule is hard to see, but our eye is drawn to focal calcifications. And if you have focal calcifications in a Hashimoto's gland, I would recommend biopsying that area because very commonly it's a papillary thyroid cancer.

The gray scale features other than the calcifications are very hard to perceive. But the calcifications serve as a very important trigger that there is an underlying papillary thyroid carcinoma. And again, here's the cancer. I think without the calcifications, it would be somewhat occult in this particular gland, blending in among the other findings.

Now, one thing that you might see is a case such as this. This is a relatively young patient who was diagnosed with Hashimoto's thyroiditis in childhood and was coming in just for a surveillance ultrasound. And the gland itself was very heterogeneous. It was normal in size. But what was quite atypical about this patient were all of these calcifications in the right lobe and no calcifications in the left lobe. And I've now seen a number of cases in which this in fact represents papillary thyroid carcinoma.

Papillary thyroid carcinoma can start as a very small focal lesion. And if it's aggressive go through the intrathyroidal lymphatics and travel through the gland. We did a blind biopsy just into the right lobe and got back papillary thyroid carcinoma.

So if you see very asymmetric distribution of calcifications in a gland, be suspicious that there is a hidden occult papillary thyroid carcinoma underlying, and this asymmetric involvement by the calcifications is your key.

Now I wanna show you this particular case. This patient was carried with the diagnosis of chronic lymphocytic thyroiditis. And she came to us, this is what her right lobe looked like here, very patchy hypoechoic areas. But again, notice these little tiny calcifications in the right lobe. This was her left lobe. Very similar appearance with some sort of irregular areas, some sort of normal areas. Vascularity, increased vascularity throughout the gland, no mass effect. Again, a finding we can see in the setting of chronic lymphocytic thyroiditis.

And here's a video clip of what the right lobe looked like, but again, our eyes were drawn to all of these little calcifications running through the gland, not something that you would see commonly in the setting of chronic lymphocytic thyroiditis. Her left lobe happened to have a mixed cystic and solid nodule here and above and beyond that, again, all of these calcifications.

But there's a very important finding on this particular video clip. And the finding is just behind the left lobe of the thyroid, right behind it. Just show you that again, right behind the left lobe. Right here in fact is an oval structure that's mixed cystic and solid right there. And what that represents is an abnormal central compartment or paratracheal lymph node that has mixed cystic and solid echogenicity, a very strong red flag for the diagnosis of papillary thyroid cancer.

And so in fact, when we looked more carefully, we went into the lateral cervical lymph node chain and we could see similar appearing lateral cervical lymph nodes. And when we biopsy these lymph nodes, they were packed with psammoma bodies and metastatic papillary thyroid carcinoma.

So this is another type of papillary thyroid cancer called diffuse sclerosing variant of papillary thyroid cancer, which overlaps in some ways with the appearance of chronic lymphocytic thyroiditis. It's not that common. It accounts for about 0.8 to 5.3% of all papillary cancers, but it tends to present in young female patients and it's most commonly mistaken for thyroiditis. In fact, these patients may be antibody positive, it can occur in the setting of underlying thyroiditis. But the key is once you identify these microcalcifications either intraglandular or very commonly in nodal metastasis, then you know you're dealing with an underlying diffuse sclerosis variant of papillary thyroid cancer.

Fortunately, these patients do very well. Their cure rate is just the same as if they have papillary thyroid cancer, but you wanna keep an eye on those calcifications and you always wanna assess lymph nodes in all patients. But particularly when you see some of these unusual findings, this was the patient's isthmus view and in fact she has two positive midline lymph nodes right there. These pre laryngeal lymph nodes were positive as well.

So just keep your eye on those calcifications and look for metastatic lymph nodes as the key to the diagnosis.

Focal Thyroiditis and Benign Findings

Now another thing that can happen, and I mentioned this before, that sometimes you'll have a relatively normal appearing thyroid that has just one nodule in it, one nodule that looks like any other nodule. And if you biopsy this, you may get back the diagnosis of focal thyroiditis. And we saw about 20 some patients and we published our results that we would have not specifically diagnosed this as a patch of thyroiditis, yet that can happen. And in large surgical series you'll see that sometimes up to 10% of focal abnormalities seemingly in an otherwise normal appearing gland can be a very focal presentation of thyroiditis. And our pathology colleagues are well aware of that.

We also, as I mentioned before, see a case like this that has very recognizable features of thyroiditis and has a dissimilar hyperechoic nodule. And in our early experience, as I mentioned before, we were biopsying all of these, but over time we've really just followed those that are small because the yield of this being anything other than a asymmetric involvement of the gland by thyroiditis was very small.

If these are larger, more irregular, if they have calcification or any other features, we may in fact opt to biopsy them. But when they're less than 15 millimeters smoothly marginated hyperechoic, we tend to just follow these because most of them are in fact just benign findings.

So here was a case I showed you before, when we see these very small hyperechoic lesions, these are leave alone quite different from this nodule. Yes, it's hyperechoic, but it's calcified. It has infiltrating margins. And this, as you may imagine, was a papillary thyroid cancer in the setting of chronic lymphocytic thyroiditis.

These generally are stable on follow up and unless they achieve large size or have another suspicious feature, we leave them alone.

And so, as I mentioned before, this is sort of our working algorithm to differentiate pseudo nodules and benign nodules in the setting of asymmetric involvement from those that we consider to be papillary thyroid cancer calcifications, whether they are focal or asymmetrically involving the lobe or an association with abnormal lymph nodes. Very important small lesions tend to be unimportant and we leave them alone.

Malignant Lymphoma

Now what about malignant lymphoma? Malignant lymphoma of the thyroid is relatively unusual, but virtually all cases that occur occur in the setting of chronic lymphocytic thyroiditis. They account for about two to 5% of all primary thyroid malignancies, and they tend to have a one of two or three different patterns.

One can just be a homogeneously hypoechoic lobe or lesion within a lobe with a lobulated margin, and they tend to have a well-defined border. And the pearl of diagnosis here is increased through transmission just like lymphoma elsewhere in the body. It sheets and sheets of lymphocytes without a lot of acoustic interfaces providing a very robust acoustic medium and very little attenuation of the sound.

So despite the fact that a patient has a very enlarged lobe in the setting of Hashimoto's thyroiditis, one that you would expect to be very densely acoustically blocking the sound, if you see increased through transmission, you have to worry that instead of being lymphocytic infiltrate in the setting of Hashimoto's with fibrosis, now you have just a uniform cellular infiltrate and to suspect lymphoma, sometimes it's much more cryptic and it's just a very asymmetric enlargement of a particular lobe, or it can be a combination of a mixed pattern of these two presentations.

Here was a patient with a 30 year history of chronic lymphocytic thyroiditis. The right lobe was extremely small, smaller than a centimeter in longest diameter. Hypoechoic very atrophic. But the left lobe was very enlarged. It measured about five centimeters in length, almost three centimeters in width. And although it was hypoechoic, we could beautifully see behind this particular lobe. Very good transmitter of sound between the asymmetry and the fact that we were seeing this increased through transmission. We did a blind biopsy of the left lobe and it revealed lymphoma in the setting of chronic lymphocytic thyroiditis.

Here you can see where we're biopsying that left lobe based on those particular features.

Another thing that we always do when we're presented with a patient such as this, is that we always look at lateral cervical lymphadenopathy. As I mentioned before, patients with Hashimoto's thyroiditis may have prominent central compartment nodes. They usually have normal morphology, but it's uncommon to have abnormal lateral cervical nodes.

This patient had longstanding Hashimoto's thyroiditis. There was sort of an unusual area here back here in the lobe, no real mass effect in the left lobe, but when we looked in the left lateral neck, there was an abnormal very rounded node. When we biopsy this node, it revealed lymphoma as to the biopsy of this area. And so this is another tip off to the presentation, and that is asymmetric lateral cervical lymphadenopathy.

Here's another patient with chronic lymphocytic thyroiditis. A very heterogeneous area that we can see in the right lobe. This was suspicious to us and we went ahead and we biopsied this area here and we also looked, and this particular patient had cervical lymphadenopathy due to her lymphoma.

Other Types of Thyroiditis

Subacute or de Quervain's Thyroiditis

I'd just like to finish up with a couple of unusual types of thyroiditis, so-called subacute or de Quervain thyroiditis. This is relatively unusual. It usually presents after an upper respiratory or other viral infection. And the patients present with symptoms, either thyroid tenderness and or systemic symptoms such as low grade fever, sore throat and so forth.

The patients may have thyrotoxicosis, but many of them are euthyroid at the time of presentation. The presentation is that of a hypoechoic and patchy thyroid that can have nodular areas. And the key is that these usually resolve, it may be very vascular, even simulating Graves disease, but in my experience, the vast majority of these patients actually have normal to diminished vascularity in the setting of subacute thyroiditis.

And usually this is a clinical diagnosis such that very few patients come to imaging, but when they come to imaging, you wanna have an appreciation for the findings.

So here was a patient who had very prototypical subacute thyroiditis on physical exam. Her gland was a very heterogeneous, it was a little bit enlarged, 6.6 millimeters, but relatively hypovascular. The patient recovered from this episode and we saw the patient a year later and a year later. Her thyroid was completely normal in size, normal echogenicity, normal in vascularity. And this has been the vast majority of patients that I have seen fall into this particular category.

Atrophic Thyroiditis

Atrophic thyroiditis is just when we refer to an end stage, very small gland that's gland only 0.8 on 1.7 centimeters in dimension, it can be of any echogenicity. We may in fact never know the cause. It could be autoimmune related, it could be due to other things. It's just a very small and atrophic gland regardless of the cause. And the vast majority of these patients, as you would imagine, are hypothyroid and have low iodine uptake.

Amiodarone-Induced Thyroiditis

One thing that ultrasound can have an important role, and that is in patients who are being treated with amiodarone for cardiac disease who become toxic and they can become toxic for one of two reasons, it's relatively uncommon. Type one is when the iodine load induces a hyperthyroidism with increased vascularity. And usually this is in the setting of underlying disease, such as already having a multinodular goiter or Graves disease.

The second is a destructive type of thyroiditis. These patients usually have a normal gland before they're treated with amiodarone. And what's happening, the gland is being destroyed and thyroid hormone is just being dumped into the bloodstream. When we look at these patients, they tend to have normal or decreased vascularity.

Now it's very hard to do a radioiodine uptake because the iodine load from the drug amiodarone is generally blocking the thyroid such that our typical I-123 scan is very hard to perform. And ultrasound becomes very important to identify those patients with increased vascularity, the so-called iodine load type, which is treated very differently from the type two, which is the destructive type. These patients often are treated with steroids. And so the distinction is purely made on the basis of how the gland appears. The type two is a much more common.

This patient was on amiodarone for several years. He had a hyperthyroidism. Very dangerous in these patients with very marginal cardiac reserve. His gland looks relatively normal, but we can say it's a gland of diminished vascularity and he can go on to be treated knowing that he has this destructive type of hyperthyroidism.

Drug-Related Thyroiditis (Interferon)

In the setting of amiodarone, we can sometimes see drug related thyroiditis. This was a patient with completely normal TSH a year earlier. He was treated with interferon for liver disease and he developed relatively rapid onset of hypothyroidism with very high TSH. He was antibody negative and here's what his gland looked like. And so this was a presumed case of interferon related thyroiditis due to drug therapy. And he was treated successfully with a repletion of his T4.

Conclusion

So in conclusion, there is a number of sonographic markers of autoimmune thyroid disease, including an enlarged gland size. Heterogeneous echogenicity, increased vascularity, but they're relatively non-specific. And overlap and clinical information is always key.

One of the important things I've hoped to present to you is the differentiation of pseudo nodules from true nodules in the setting of patients with autoimmune thyroid disease, particular Hashimoto's thyroiditis and some clues that can differentiate between the two.

We pay a lot of attention to focal calcifications and asymmetric calcifications for occult thyroid cancer, particularly papillary thyroid cancer and unilateral lateral compartment lymphadenopathy is important both for the detection of lymphoma as well as for metastatic disease in the setting of sclerosing variant papillary thyroid carcinoma.

So I think nodular disease, nodules in fact are quite different looking and sometimes we can pick out nodules that are likely to be cancer in the setting of diffuse disease. I think there's just very subtle differences and overlap. But it's a very nice challenge for me to examine these patients and try to be useful in trying to identify some of the complications and some of the non suspicious findings.

Thank you very much.