Sonographic Evaluation of Patients Following Thyroidectomy for Cancer - SD

Introduction

I am Joe Langer from the University of Pennsylvania Medical Center and I'll be speaking on sonographic evaluation of the neck in patients following thyroidectomy for thyroid cancer.

Hi, I am Joe Langer and I'm going to be speaking about sonographic evaluation of patients following thyroidectomy for thyroid cancer.

Learning Objectives

The learning objectives will be to explain the rationale and technique for using sonography to assess the postoperative neck, to recognize the sonographic appearance of abnormal lymph nodes and thyroid bed recurrence and to recognize normal and non-malignant postoperative changes in the neck.

Thyroid Cancer Recurrence Data

Now if we think about thyroid cancer, perhaps the best data has come from this paper in the Mayo Clinic that reviewed their experience with close to 2,400 patients over a 60 year interval.

And as we can see, approximately 10% of patients developed cervical lymph node recurrence and approximately 6% developed either local recurrences in the neck or distant metastases.

So if we focus in on disease within the neck, that comprises approximately 78% of all recurrences in patients with thyroid carcinoma.

Methods to Detect Thyroid Carcinoma

Now the methods available to detect thyroid carcinoma are both clinical and imaging. On the clinical side, there's physical examination of the neck to determine lymphadenopathy or masses within the thyroidectomy bed, as well as laboratory analysis of the serum thyroglobulin, a hormone produced by thyroid tissue.

In patients who have had thyroidectomy for thyroid cancer, typically the remnant of the thyroid is ablated killing all normal tissue such that an increase in this protein thyroglobulin would therefore be due to cancer recurrence.

This can either be a resting level or the patient can be given artificial injections to increase the level and then detected by a serum test.

On the imaging side there's whole body iodine, 1 31, scan neck, ultrasound neck and or chest ct neck. MR. And PET scan.

Focus on Whole Body Iodine Scan and Neck Ultrasound

I'd like to concentrate on whole body iodine 1 31. Scan and neck ultrasound for just a moment, because these have been the mainstay for evaluation of the neck over the last 40 years now until 2003, most investigators and researchers in the field thought that the I 1 31 scan was a very good test for detecting thyroid recurrence in the neck.

But in fact this paper by Fassil Dotti published in cancer in 2003 illustrated that a elevated serum thyroid globulin level of over 10 detected 45% of neck recurrences.

Whole body scan detected only 28% of neck recurrences, but neck sonography detected 94% of recurrences.

And this work was then repeated by a number of other authors, again comparing directly in the same patient population.

Whole body scan depicted in red as compared with neck sonography.

And you will note that in each of these series the whole body scan detected less than 50% of the metastases, whereas neck sonography detected between 70 and close to 100% of these recurrences.

Therefore, we now know that whole body scan detects far less than 50% of thyroid cancer metastases that is, many of them are not iodine avid.

These metastasis are therefore neither detectable nor treatable by I 1 31 and sonography has replaced the whole body scan now for detection of local recurrence and neck surgery has replaced I 1 31 treatment for these recurrences.

Advantages of Sonography Over Other Imaging

Now if we think about next sonography, we have a number of advantages over other cross-sectional imaging of the neck.

There's much higher resolution with sonography as compared with CT and MRI exams.

It allows detections of nodes that are normal in size but display subtle abnormal sonographic characteristics.

It's relatively inexpensive and readily available.

And additionally, when nodes are detected sonographically, a biopsy can be performed to confirm the suspicion that the node is abnormal.

Limitations of Sonography

Of course, there are several limitations.

Sonography is operator dependent.

It's limited to only evaluation of the neck and the upper mediastinum and therefore unable to detect distant metastases.

Even some neck nodes may be obscured by overlying structures such as those that that lie deep within the pharyngeal space and in the lower mediastinum.

Additionally, sonography is limited in its ability to detect invasion into the trachea and the esophagus and for an invasive tumor, either CT or MRI of the neck would be needed to detect this type of thyroid cancer involvement.

Questions on Sonography Use

So we're left with a few questions.

Who should undergo next sonography following thyroidectomy, when should it be performed and what findings are important in order to detect recurrence?

Risk Factors for Neck Recurrence

Well, the risk factors for neck recurrence include large tumor size, aggressive histologic features, extra thyroidal extension as determined by pathology positive lymph nodes at the time of diagnosis and age being under the age of 16 or over the age of 45 years at the time of diagnosis.

However, the vast majority of patients who do develop recurrent disease in the neck have none of these features and are considered relatively low risk or recurrence.

And this is because this group of patients comprises the largest group of patients with thyroid cancer.

Recurrence in Low-Risk Patients

In fact, in a paper published in the Journal of Endocrinology and Metabolism in 2004, a series of 493 patients who are considered low risk for recurrence, with papillary thyroid cancer were followed for five years with neck sonography, serum thyroglobulin and whole body scan.

38% did develop neck recurrence after one year, and this was documented by ultrasound guided lymph node biopsy.

In this series, the whole body scan missed 36% and th globulin analysis missed 18%.

This establishes the role of ultrasound as the most sensitive technique in this low risk population.

Additionally, there was a relationship between the level of thy globulin and the size of the positive lymph nodes and importantly a negative ultrasound coupled with a negative thyroglobulin had a very low risk of recurrence, close to zero, very reassuring and allowing the patients to undergo less invasive and costly diagnostic testing.

Recurrence Rates After Initial Therapy

Now if we look at the recurrence rates after initial therapy, we can see that the vast majority of recurrences occur in the first 10 years with the disease recurrence rate falling sharply off, after that time and therefore most concentration of the examination is performed within the first 10 years following thyroidectomy.

ATA Guidelines and Protocol for Sonography

If you look at the A TA guidelines for who should have next sonography, basically the guidelines say that at six and 12 months and then annually for at least three to five years depending on the patient's laboratory analysis.

In our lab, the protocol that we use is if the patient has either residual disease or an elevated serum thyroid globulin or high risk pathology such as positive lymph nodes, vascular invasion or an aggressive histology, we see them back in the first three to six months after their surgery and perhaps supplement the ultrasound exam with chest CT and PET CT for some of the more aggressive tumors.

For those patients who are not known to have residual disease or an elevated serum th globulin, we see them in the first six to 12 months after ablation and then annually for at least 10 years.

Lymph Node Anatomy and Compartments

Now when we think about lymph nodes in the neck, many of us think about these descriptive terms in terms of where the lymph nodes lie within the neck, but the head and neck surgeon has a very different perspective on the neck heath or she thinks of the neck as having compartments.

The central compartment which contains the thyroid parathyroid glands, para tracheal and upper mediastinal lymph nodes, and then the lateral compartments of the neck on both the right and the left side, often referred to as the anterior and posterior triangle lymph nodes.

Detailed Nodal Classification

Let's look at this in more detail.

A landmark paper by SOM published in HAR in 2003 in fact used this nodal classification that the surgeons rely on as an explanation for how to figure out where the nodes are within the neck such that the head and neck surgeons and the imagers could easily identify the compartment involved.

The neck is essentially divided into the central compartment which comprises level six and seven and the lateral neck which comprises compartments one through five for thyroid cancer involvement of compartment one is relatively rare, so we will not discuss that at this time.

Pertinent Anatomy for Compartments

So to review the pertinent anatomy for deciding which compartments of the neck nodes are in, one needs to make note of three important landmarks, the hyoid bone, the cricoid cartilage, and the sternal notch along the lateral compartment.

We wanna pay attention to the common carotid artery depicted in red, the internal jugular vein depicted in blue and the lateral posterior border of the sternal CTO mastoid depicted in yellow.

So when we talk about the central neck, were level six and seven, we talking about the nodes in the central compartment of the neck below the level of the hyoid bone and extending into the upper mediastinum below the level of manubrium.

These are called level seven nodes.

Again, it's important to note that the hyoid bone is the upper border for this central compartment.

The lateral lymph nodes or lymph nodes two through five are found laterally within the neck.

Again, looking at the level of the hyoid nodes that are above the level of the hyoid but situated laterally are level two lymph nodes.

The margin of the cricoid therefore divides the anterior triangle of the neck into level three and level four nodes, and the nodes that are situated lateral to the sternal colleto mastoid or the posterior triangle nodes are levels five A and five B with this division established by the border of the cricoid cartilage.

So again, this anatomy is very important when communicating with our surgeons as to which compartments are involved, whether it be the central neck level six and or seven, the lateral neck often levels two through five or a combination of the two in order that the surgeon may know where the lymph nodes lie.

Where Lymph Node Recurrences Occur

Now if we look at where lymph node re, recurrences are likely to come, we have data from two sources.

The first is in patients who undergo reoperation following thyroidectomy and there's also a large body of literature that looks at lymph node involvement prior to any thyroid resection in this paper published in 2002, we can see at the time of presentation that ipsilateral central neck was the most common followed by contralateral central neck, but also ipsilateral lateral neck involvement was very common and least common was contralateral lateral neck.

If we look at their series of patients who have recurrent disease at operation, we can see that the recurrent patients have a very similar distribution of nodal involvement.

Again, there's a positive correlation between tumor size and lymph node positivity and the ipsilateral compartment is as likely to be involved as the central neck, although the contralateral lateral neck is least likely to involve.

In fact, it is involved in as much as 10% of patients and should be examined routinely in patients undergoing sonographic surveillance.

This also highlights the point in patients prior to surgery that it's very important to identify suspicious lymph nodes at the time they're being diagnosed with their thyroid cancer.

If there is positive lymphadenopathy, these nodes should be biopsied and the patient should undergo a modified radical neck dissection at the time of thyroidectomy.

This will remove disease that may be non iodine avid and spare the patient future surgery.

In fact, many involved lymph node in the lateral compartment may in fact not be recurrence as originally thought, but may be persistent disease following thyroidectomy in patients who have non avid iodine avid disease.

The emphasis for this comes from the same pattern of nodal involvement in the pre thyroidectomy patient as well as the patients developing recurrence in the neck.

Clinical Identification of Nodes

Now it's important again to identify these nodes clinically.

If patients are known to have positive disease at the time of presentation, we know that their survival is affected.

Those who have no palpable lymphadenopathy at the time of diagnosis have a relatively low rate of local and nodal recurrence as compared with those patients who in fact have clinically palpable nets at the time of presentation.

Additionally, in those patients who have had surgery, the disease free survival is excellent for those patients who have negative lymphadenopathy by sonographic exam and for those patients who have ultrasound positive lateral lymphadenopathy, we can see the survival falls.

There was no impact of central lymphadenopathy detected by sonography in these patients.

Technique for Scanning Lymph Nodes

Now let's talk a bit about the technique.

How is it best to look for abnormal lymph nodes within the neck?

It's important that you use a high resolution transducer 10 megahertz or higher.

You wanna use a le linear configuration for the best detail.

You may, however need to use a smaller probe for evaluation of the inferior central compartment of the neck and the upper mediastinal placing the small probe right at the sternal notch and angling down into the upper mediastinum and color doppler is essential for assessment of the vascularity of these nodes as we will discuss in a little bit.

Also, patient positioning is very important.

It's very important to hyperextend the neck often by putting a pillow behind the shoulder blades, a patient can achieve very profound extension, allowing evaluation of the entire neck.

When we do our scan, we wanna look from the submandibular area all the way down to the borner of the sternal clat mastoid along the internal jugular chain and in the supraclavicular region.

We wanna sweep laterally along the border of the bone to evaluate the whole supraclavicular fossa in the posterior triangle.

We wanna put our probe as far back as the mastoid and scan along the imaginary line of the spinal accessory nerve between the lateral border of the subclavian and the trapezius.

We wanna look at the parat tracheal region from the level of the cricoid bone down to the sternal notch and angle into the upper mediastinum.

As I explained earlier, now within the neck it's very common to see cervical lymph nodes.

In fact, over 300 lymph nodes are present on histology.

On sonography, one typically visualizes between eight to 25 nodes with no difference, among age, gender, or ethnic distance.

Normal Lymph Node Size and Appearance

Now the, the size of the normal lymph nodes varies with location and age.

In the upper neck in the submandibular region, it's very common to see larger nodes because these nodes drain the oral cavity.

It's also common that the nodes are smaller in younger patients than older ones and that fatty infiltration occurs with age causing nodes to sometimes be larger and quite prominent, but otherwise graphically normal.

So here are a variety of normal appearing lymph nodes and as we can see, some of these in fact have very marked fatty replacement in the, in the hilum, including this last node that's displayed in an 80-year-old patient.

Evaluating Cervical Lymph Nodes

Now when we look at cervical lymph nodes, it's important to evaluate the shape and size of the lymph node.

A normal lymph node is oval or kidney being shaped.

Often the short to long axis is very small, measuring under 0.5 as a lymph node becomes involved with metastatic disease, the tendency is for the lymph node to become rounded and the short to long axis to increase to over five.

However, a normal variant can be increased in the size of the axis of the short to long axis ratio.

And this is quite commonly seen in the submandibular region.

Often the central compartment lymph nodes are quite small and least commonly seen.

So an increased size or rounding of these lymph nodes, is often a very suspicious sign for metastatic disease.

So here's a very normal appearing lymph node.

The short to long axis in this case is 0.75.

The lymph node has a very nice oval appearance and a prominent fatty hilum.

This would be considered a normal lymph node.

Now the abnormal shape or size alone is not very reliable as an isolated feature, the false positive rate is as high as 15% and the false negative rate as high as 20%.

As I mentioned before, it's particularly important when evaluating the central compartments of the nodes.

Generally a node in the central compartment that has a six to eight millimeter short axis or higher is abnormal and as we'll talk in great detail rather than size, it's the sonographic features of nodes, particularly cystic change, calcifications and vascularity that are much more important than the actual size of a lymph node.

Here we have the central compartment longitudinal view.

We can see the esophagus down below and we can see a lymph node outlined by electronic calipers right here.

This lymph node is relatively hypoechoic, but importantly when we measure it, we can see that the short to long axis ratio is elevated over 0.5.

This node is rounded as evidenced by this abnormal ratio and this node was biopsy proven recurrence in this patient with papillary thyroid carcinoma.

Here we have a node that is rounded, however normal.

This is a submandibular lymph node or a level two lymph node.

And again, these nodes high in the neck are very commonly enlarged and rounded in shape and in this particular location.

In the absence of other sonographic abnormalities, this particular appearance is not considered suspicious for metastatic disease.

Specific Features of Abnormal Lymph Nodes

So the features we're going to talk about specifically are the presence or absence of the hilos cystic areas, calcifications and abnormal vascularity.

If we look at a diagram of lymph node, we can see that the hilum is the area where the vessels enter.

There's fibro fatty connective tissue and that the lymph nodes, uh, ductule drain into the periphery such that metastatic disease is carried by the lymphatic channels to the periphery, whereas the vascularity enters from the center and then branches becoming smaller over time.

So when we look at the vascularity of a lymph node, we expect to see the hilar vessels and relatively little peripheral vascularity in a normal lymph node.

When we look at lymph nodes that don't have a fatty hilum, this is somewhat of a subjective finding, but at least in one paper it carried a 92 positive predictive value for metastatic thyroid carcinoma.

What's happening here is that tumor deposits are obliterating the normal architecture of the node causing that connective area within the hilum to be less visible.

You have to be careful, however, because in some small nodes, the hili in fact may not be visible in the node that is otherwise unaffected by metastatic disease.

Cystic Change

One of the most important findings we look for is cystic change and this reflects the tendency of papillary carcinoma to undergo cystic degeneration.

The affected nodes may contain small isolated cystic areas, multiple scattered cystic regions, or may be in fact entirely cystic.

The differential would include necrotic nodes from squamous cell carcinoma of the head and neck, sometimes inflammatory disease and some congenital cysts such as brachial cleft cysts.

Here's an example of a metastatic node from papillary thyroid cancer that has a large cystic component in the center with some peripheral hypoechoic material and that you'll note that there is vascularity within that.

Here's another node that's in fact quite large, measuring over two centimeters in size.

It has a cystic component and a solid component, and the solid component is highly vascularized.

In this patient who had a palpable lymph node from metastatic papillary thyroid carcinoma, a chain of lymph nodes may demonstrate very variable degrees of cystic change from a node that's almost all cystic to a node that's mixed cystic and solid to a node that has a smaller solid component.

Again, you will note that the solid component is highly vascularized in each of these metastatic lymph nodes.

Some nodes in fact may have colloid reverberation artifact within them having mixed cystic and solid components.

Calcifications

Nodal calcifications are another very important finding and are noted in between 50 and 70% of patients with papillary thyroid carcinoma metastasis and are also noted in medullary cancers that have metastasized to lymph nodes.

The calcifications can be quite large and dystrophic or maybe small in punctate.

Differential diagnosis for calcified lymph nodes in the neck would include tuberculosis, sarcoidosis and changes following radiotherapy of other head and neck malignancies.

Here is a solid lymph node with echogenic material and scattered small calcifications.

Hyper echoic Foci

Hyper echoic foci are another important finding and these these may vary from very small echoic foci within the periphery or diffuse replacement of a lymph node by echoic material.

Here we can see a series of lymph nodes with each lymph node nearly entirely replaced by a very large amount of echoic material reflecting tumor deposit.

Within these involved nodes, perhaps one of the most subtle findings is an increased focus of peripheral hyper echogenicity.

Often in combination with increased vascularity we can see a lymph node that's relatively normal in size and the more proximal aspect of this lymph node is relatively normal in appearance with an echogenic fatty hilum.

But inferiorly we can see that there's a focus of increased echogenicity and when we use color doppler to evaluate this area, this exactly corresponds to an area of increased vascularity.

This it was a biopsy proven involved lymph node.

The majority of the lymph node was normal, but this was a small metastasis to lymph nodes and ultrasound's.

Very excellent spatial resolution coupled with color Doppler analysis allows us to detect these very small volume, metastases to lymph nodes pathologically in another patient.

This is what an involved lymph node may look like.

The majority of this lymph node has normal echo texture, but here in the periphery of the node we can see involvement by cancer and this what histologic.

This histologic example would correspond to a case such that I just showed you with again a peripheral deposit of tumor arriving from the ductules to the periphery of a lymph node.

Abnormal Vascularity

In order to detect this small vascularity, we have to optimize our parameters to be able to detect low velocity flow.

We need to use a low wall filter, A PRF of 800 hertz or lower and we wanna look carefully in the periphery of these nodes for either focal or diffusely, increased vascularity or perhaps abnormal appearance to the vessels that we see that have an irregular course or irregular borders.

Again, a lymph node that has some hyper echoic foci, but with color doppler we can see very large irregular aberrant lymph nodes, not the normal hilar lymph nodes in this node with biopsy proven metastatic thyroid carcinoma.

Now sometimes we'll see involvement of the larger vessels which could either be compression as is typical with papillary thyroid carcinoma.

Here's an abnormal lymph node that has multiple hyper echoic foe and you can see this has mass effect on the adjacent jugular vein compressing it.

Sometimes we can see anxious involvement of the vein itself.

There's an echogenic lesion here within the internal jugular vein, which on color doppler has internal vascularization representing vascular extension of a follicular carcinoma of the neck.

Thyroidectomy Bed Evaluation

When we look in the thyroidectomy bed, it's normal to see some echogenic material representing the normal connective tissue.

Here we see the trachea and the common carotid artery on the right and this amorphous echogenic material representing fibro fatty connective tissue on the left hand side.

Very similar echogenic connective tissue between the trachea and the common carotid artery.

And this is a normal postoperative finding within the thyroidectomy bed.

We may either see a bed recurrence or central lymph node recurrence.

The bed recurrence will appear as a soft tissue mass in the thyroidectomy bed, often very vascular.

Remembering that it's fairly unusual to see normal perticular level six lymph nodes.

We will be looking for small lymph nodes within the central compartment, considering them somewhat suspicious.

Here's a patient who had a thyroidectomy.

We can see the right side of the thyroidectomy bed is relatively normal.

Here's the trachea and here's a relatively large soft tissue mass in the left thyroidectomy bed that is highly vascular representing a thyroidectomy bed recurrence.

In this patient In the central compartment we see a lymph node here that's relatively small and minimally vascular, but more inferiorly we see a lymph node that measures over seven millimeters in maximal diameter and is of increased vascularity.

Both of these nodes were positive.

The smaller node draws suspicion again occurring in the central compartment of the neck in the area where it's less common to see normal nodes.

So although this node is relatively small in size and not particularly vascular, its appearance is somewhat suspicious.

This larger node with higher vascularity is a very high suspicion in this patient with medullary thyroid carcinoma.

Here's a lymph node that's highly hypoechoic and highly vascular, again representing a central compartment lymph node.

From a practical standpoint, sometimes it's difficult to distinguish metastatic lymphadenopathy in the central compartment from thyroid bed recurrence.

However, the treatment which is surgery in the vast majority of the patients is the same, such that this distinction may not be clinically relevant.

Hidden Areas for Metastatic Lymphadenopathy

Now we've discovered a few places where we know that metastatic lymphadenopathy likes to hide.

I think more aptly. These are just areas of the neck which you may pay, which you need to pay careful sonographic scrutiny to in order to detect these nodes.

The first is above the thyroid.

There can be pretracheal lymph nodes extending above the thyroid that may have not been surgically resected.

The second place is along the sternal mastoid muscle where it joins with the clavicle.

This is an area that's somewhat difficult for the surgeons to resect and is somewhat difficult for the ologist to examine due to the overlying bone.

And the last is in the upper mediastinum.

Similarly difficult for the surgeon to access and difficult for the sonologist to image in all patients.

Here's a patient who had a persistently elevated thro globulin and a normal stenographic evaluation of the upper neck.

But when we angled our transducer down into the upper mediastinum, we could see the soft tissue mass adjacent to the trachea.

And in fact, this represented an over two centimeter in size nodal recurrence into the upper mediastinum.

Ultrasound-Guided FNA for Abnormal Nodes

Now if we detect an abnormal node and sonography, we can do an ultrasound guided FNA and in certain situations we can also send the material we obtain for thyroid globulin analysis to confirm that it is in fact metastatic papillary thyroid carcinoma.

We do our technique of FNA of these nodes very similar to thyroid nodules.

Again, emphasizing that patient positioning is extremely important.

As often these are very small targets.

We use aseptic technique, a 25 gauge BD needle with attached to a 10 cc syringe and do one pass with just gentle motion of the needle tip into lymph node.

However, with coupled with aspiration, if the node is predominantly cystic, here's a video clip of such a procedure.

We can see the common carotid artery, the jugular vein, a lymph node relatively small in size but was abnormal because it had hyper echoic foci and we can see the needle being gently advanced into this lymph node with very mild aspiration.

In order to obtain enough cells for cytologic analysis, sometimes papillary thyroid carcinoma can be an entirely cystic lesion such as this.

In this instance, it's very difficult to get cells for cytology and so we would do an attempted cytology, but then we would aspirate the node sending the aspirate.

For thyroglobulin analysis, you would wanna distinguish all cystic lesions in the neck from congenital cysts, which have a slightly different location.

The brachial cleft cyst is typically anterior to the sternal cided mastoid as well as parathyroid cysts, which tend to contain entirely clear fluid.

If there's any doubt analysis by thyroid globulin, assay is the single way to determine if in fact it is a metastatic lesion from papillary thyroid carcinoma.

Pitfalls in Sonography for Neck Recurrence

Now, there are some pitfalls to the use of stenography for detecting neck recurrence, such as inability to visualize some nodes that either lie behind the pharyngeal structures or very low in the mediastinum.

There are some normal structures which can be mistaken for disease.

If one is not familiar with the anatomy, there are some postoperative changes such as scar tissue, neuromas and low grade inflammatory lesions.

And again, these very small micro metastasis may be so small that they're difficult to detect by sonography.

There are a few things that, knowledge of of these as normal structures will avoid pitfalls.

Normal Structures Mimicking Disease

This is what the normal thyroid cartilage looks like on the right and on the left.

It can, it can be identified by its hyper echoic internal consistency and a very sharp echogenic line as well as its sort of bow shape.

Often there can be hypoechoic areas within the cartilage and these normal structures should not be mistaken for an abnormality in these post thyroidectomy patients.

Something that you'll see in younger patients, young adults and children is cervical thymic tissue.

Here is a transverse view of of the thymic tissue and then a longitudinal view.

The thymus has a characteristic appearance of a relatively hypoechoic geographic soft tissue lesion, often with these punctate little echogenic dots representing, vascular spaces and adipose tissue at mixed with the thymic tissue.

Residual Thyroid Tissue

In some patients you may see some residual thyroid tissue, particularly in the left thyroidectomy bed.

The surgeons often leave a very small amount of tissue as they're dissecting the thyroid off of the recurrent laryngeal nerve.

And so in some instances, the surgeons may leave more tissue than they would have liked, and you can see a small amount of tissue in this location.

This is particularly common in patients who have thyroidectomy.

That is subtotal.

Many patients have no known primary thyroid cancer prior to having their thyroid removed and would have a subtotal thyroidectomy.

The pathology may indicate that these patients have tumor and therefore they may be subsequently referred for next sonography.

In such patients or patients who have a relatively small tumor under 10 millimeters, the patients may not undergo radio iodine ablation and therefore may have thyroid tissue.

Over time, this tissue may regrow and simulate a recurrence.

It may be quite difficult to distinguish this from a true recurrence.

Often these areas are not particularly vascular, but when in doubt a biopsy and analysis of the tissue may be necessary.

Here we see such a patient here is the trachea, and here we see a hypoechoic lesion in the left thyroidectomy bed that's not particularly vascular.

This was biopsy proven regrowth of tissue in a patient who had had a subtotal thyroidectomy five years earlier.

Other Postoperative Findings

This was a patient who had had a thyroidectomy for thyroid cancer and we saw an abnormality in the central compartment of the neck.

This was considered suspicious for papillary thyroid recurrence given its size.

It was also noted to be highly vascular.

However, on biopsy this proved to be a parathyroid adenoma In its typical location, there would be no way to prospectively distinguish between these two entities.

This is a patient who had an amorphous area of soft tissue, quite remote from the common carotid artery, but it was a soft tissue abnormality.

The patient, in fact did have an elevated serum thyroglobulin and had tall cell papillary thyroid cancer, a relatively aggressive subtype.

So the pretest probability of having a recurrence was relatively high.

When we attempted an FNA of this lesion, the patient experienced severe pain and we were only able to get a small amount of fibro connective tissue.

We diagnosed this therefore presumptively as a post-surgical neuroma based on the clinical and imaging features.

And this has now been a stable finding for over five years.

And in fact, these are quite common to have post-surgical neuromas in and around the neck.

The typical sonographic appearance is an ill-defined soft tissue lesion.

It's usually avascular, no cystic areas or calcifications are identified, and one key is its location, relatively remote from the carotid artery.

And in jug jugular vein, most lymph nodes are in close proximity to these two vessels.

So the appearance of this out remote from those structures was a tip off, and most importantly, these are often painful to the touch and or elicit a large amount of pain when biopsy is attempted.

If in doubt, they again, they can be followed over time to assure that they're not a growing abnormality.

In this particular patient, an abnormality was detected in the left thyroidectomy bed, but the patient was at relatively low risk with a normal thyroglobulin.

At first glance, these echogenic foci were thought to potentially represent calcifications within a lymph node.

However, on further analysis, we realized that there was dirty shadowing, raising the possibility that in fact, this represented air on further detailed evaluation, we were able to demonstrate a small communication from this structure to the underlying cervical esophagus.

And a baram minimus, a barium, upper GI examination subsequently revealed that in fact, this abnormality was a zinc's diverticulum of the cervical esophagus.

In a number of patients, we've seen complex collections within the thyroidectomy bed in patients who have no clinical signs or symptoms of infection, and these have proven to be culture negative foreign body granulomas that may be forming around suture material left behind.

These lesions may be quite large hypoechoic and may have hyper echoic foci in interior interiorly within them thought to be suture material left behind.

Summary

So in summation then lymph node assessment plays an integral component of evaluation of patients with thyroid carcinoma.

The size of the lymph node is perhaps the least important feature, particularly when dealing with lateral compartment lymph nodes.

The shape and the internal architecture are the most important, particularly the presence of calcifications, cystic change and hyper echoic foci.

Color doppler is very important for identifying subtle metastasis that may appear as diffuse abnormal vascularity or may be in concert with hyper echoic foci, particularly within the periphery of lymph nodes.

Papillary thyroid cancer has a variety of appearances from all solid with calcifications to mixed cystic and solid to entirely cystic and appearance.

The entirely cystic lymph node poses a bit of a challenge, but with thyroglobulin analysis of the aspirate, the diagnosis can be made quite easily.

Thank you.