Thyroid and Parathyroid - SD

Introduction to Thyroid and Parathyroid Ultrasound

I am Carl Redding.

I work at Mayo Clinic in Rochester, Minnesota.

We'll be talking today about thyroid
and parathyroid ultrasound.

The superficial soft tissues of the neck can be seen
with remarkable clarity using ultrasound.

Today, we'll focus on the thyroid and parathyroid.

And specifically we'll look at nodular thyroid disease,
which is the most commonly encountered pathologic process in
this gland. We'll concentrate on a pattern based approach,
which is a practical method to distinguish those nodules
that have a malignant appearance
and require fine needle aspiration from those
that have a benign appearance
and do not require fine needle aspiration.

We'll also see in parathyroid disease
that parathyroid adenomas can be localized
with a high degree of accuracy
and we'll begin with a thyroid gland.

Perspectives on Nodular Thyroid Disease

As we do, we need to obtain a perspective on
nodular thyroid disease.

And the first perspective is
that thyroid nodules are very common.

In fact, this has been called an epidemic by ultrasound,
by some, by palpation.

These are present in 7% of the population by imaging
by ultrasound 40%,
and at autopsy, 50% of individuals will have thyroid nodules
at the same time clinically significant.

Thyroid cancer is very rare.

This is found at autopsy in 2% of the population,
but it's only diagnosed clinically in 0.2%
or two out of a thousand individuals.

And is the cause of death in only 0.005%
or five out of 100,000?

So just as there are very many benign nodules
for the few malignant ones,
there are many malignant nodules.
For the few clinically significant malignant ones,

There has been some concern
that there's an increasing incidence
of thyroid cancer in the United States.

This recent article in jama, it showed
that in the last 20 years there's been over a twofold
increase in, thyroid malignancy.

However, the conclusion was
that this reflects an increased detection
of subclinical disease
and not a true increase in the occurrence of thyroid cancer.

Also, at the same time
that this incidence has been increasing,
the mortality rate remains very low
and has been stable throughout this time.

And this is because, most
of these thyroid cancers detected in North America are a
benign variety, well differentiated papillary,
or at least not an aggressive malignancy that accounts
for about 85%.

A similar study in Korea showed that 95% of cancers were
of the papillary type.

And this is almost always an indolent
and benign acting form of malignancy.

It's not like, most other cancers like colon
or breast, where early detection is very important.

Here, the window of curability is much longer and
therefore that is why these are a benign acting
form of malignancy.

A third perspective is that the aggressive FNA management
of nodules is quite costly in our practice.

A fine needle aspiration
and the cytologic interpretation is $1,500.

Also, 20% of these reports are going to be non-diagnostic
and there's variability in the cytologic report.

It may say follicular cells present cannot exclude
follicular neoplasm.

It's estimated that just the act of going
and doing a fine needle aspiration on a thyroid nodule
that 10 to 20% of those individuals will then go on
to have surgical removal at a cost of $20,000.

And 60% of those nodules
that are removed will end up being a benign nodule.

Also, 5% of patients have some morbidity from the surgery,
either nerve injury, chronic pain hypoparathyroidism.

So given that our goals
of thyroid nodule evaluation should be certainly
to identify masses likely to be cancer,
but for the majority of patients, reassure them
that they don't have cancer and try to avoid an invasive
and costly workup including additional imaging,
fine needle aspiration and surgical excision when possible.

Pattern-Based Approach to Thyroid Nodules

So the options for thyroid nodule evaluation is
that one can look at the size of the nodule
or the appearance of the nodule or both.

In our practice, we tend
to concentrate primarily on the appearance of the nodule.

We realize that if a nodule is malignant,
there's a slightly worse survival with large nodules.

But given that we tend to concentrate primarily on
that nodule appearance,
probably the best article recently on the various
sonographic appearances of thyroid nodules, was
by Moon and radiology.

Last year, they looked at nearly
1000 nodules in the Korean thyroid study group
and very carefully looked at each specific feature
of these benign and malignant nodules.

In our practice, we tend to look at a constellation of
of features and put these together into specific types
of patterns that suggest a nodule is malignant or benign.

Another way to think of this is
that there are many thyroid nodules
that we will all encounter in our practices
and what we're going to concentrate on today is the
low hanging fruit.

These would be those that one would always
or never do fine needle aspiration on.

We realize there will be other nodules
that wouldn't clearly fall into a specific pattern
and might sometimes require FNA,
but we'll concentrate today on the low hanging fruit.

So let's look at appearances that would either come
to find needle aspiration
or not come to find needle aspiration.

Malignant Appearances Requiring FNA

And a typical appearance of a type of nodule that would come
to aspiration would be the solid nodule in the
isthmus of the thyroid.

It causes some bulging of the capsule because of mass effect
and there are tiny punctate echogenic foci within it.

And this is highly likely to be carcinoma.

When one encounters a hypoechoic solid nodule
with these fine calcifications that is going
to be papillary cancer with a high probability.

Sometimes there won't be posterior acoustic shadowing
unless the calcifications are clumped together.

These tiny echogenic foci microscopically are believed
to be, they're called Sam bodies.

They're calcified laminated spial
that the pathologists can see.

They're present in about 50%
of papillary cancers on real time.

We can see that these have a punctate echogenic,
appearance within the thyroid nodule.

Sometimes we'll see some faint shadowing if these are
clumped together,
but they're scattered throughout this
large papillary cancer.

Even when nodules are small, less than a centimeter,
when they have microcalcifications,
they have the typical appearance.

These would usually require fine needle aspiration
and generally would come to FNA in our practice.

A second type of appearance that always comes
to find needle aspiration is the nodule that is solid
and hypoechoic and has coarse
or larger calcifications within it.

And that's probable carcinoma.

These course calcifications can be seen in papillary cancer.

It's a dystrophic type of calcification or medullary cancer,
and that appearance indicates malignancy
with a moderate probability.

Our suggested dictation then when we encounter a mass such
as this hypoechoic solid mass with either coarse
or microcalcifications, we say that
that appearance is suspicious for a malignant lesion such
as papillary cancer and FNA is recommended
for further evaluation.

A third type of appearance that comes
to fin needle aspiration is the nodule
that is solid in appearance, often more homogeneous
and surrounded by a thin peripheral halo.

This is going to be follicular neoplasm
with a high probability.

Usually these are homogeneous
and solid, most of them are oval or round.

They can have a thin peripheral hypoechoic capsule.

We can perhaps see this best in real time
where the homogeneous mass is surrounded by a thin capsule.

Other times internally the mass is more heterogeneous,
but still it has that often oval appearance
and a thin capsule that surrounds the entire mass.

If we see a mass such as this,
then we would do find needle aspiration.

You can see the needle being inserted from the right hand
side of the screen, moved back and forth in a rapid fashion.

It obtains small fragments of a tissue, a material
for cytologic analysis.

This is then expelled onto a slide.

And what the pathologist sees are many normal appearing
follicular cells, but they're more tightly clumped than one
would see in just a benign type of aspirate.

And the pathologist would then say that this is consistent
with follicular neoplasm.

They can't distinguish follicular adenoma from follicular
carcinoma by the FNA alone.

So surgical excision is generally recommended
for further evaluation to exclude carcinoma.

When the surgeon excises a nodule such as this, what they,
what the pathologist does is then finally sections this into
thin sections and examines the capsule of the nodule.

They look for evidence of capsular
or vascular invasion, which would be a sign of malignancy.

And statistically more than 90% of these are going
to be benign, but some will be malignant,
usually a low grade malignancy when evidence
of this capsular or vascular invasion is identified.

So if the nodule looks like a follicular neoplasm,
why do we even do the fine needle aspiration?

It turns out that about 20% of the time the FNA will be read
as negative and the workup then can stop.

These are usually the macro, follicular follicular neoplasms
and they are benign acting
and the pathologist in looking at the slides will just say,
this looks like a negative.
Aspirate.

On the other hand, they may say this does look,
like follicular neoplasm can be a follicular
variant of papillary cancer.

It can have a very similar appearance
or perhaps be non-diagnostic.

In many cases, these will go on to surgical removal,
but they may be observed or followed up clinically.

If you have a patient with multiple comorbidities,
if the patient is elderly, it might make more sense
to follow than to remove these for the low chance
that they are malignant.

And our suggested dictation, when we see a mass such
as this, a solid moderate to large homogeneous mass,
we would say that the appearance is indeterminate.

FNA could be done for further evaluation knowing
that most many of these will be benign,
but some could be malignant.

So we've looked at several types of appearances
that would suggest that a nodule is malignant
and they should go on to have fine needle aspiration.

Benign Appearances Not Requiring FNA

There are also appearances that suggest
that the nodule is benign
and that they don't need fine needle aspiration such
as this patient who has multiple small predominantly cystic,
non palpable nodules in the thyroid.

These indicate benign OID nodules.

They may be completely anti coic.

They may contain internal debris,
they may have small echogenic foci within them,
and all of those appearances are very typical
of these colloid nodules.

In addition, we'll also see com tail artifacts
behind these echogenic foci within the fluid within these
nodules, they're probably, it's probably some sort
of crystalline material
or other material giving this reverberation artifact,
much like the cholesterol microcrystals
that are seen in the gallbladder
and give a similar type of comet tail
or reverberation artifact.

One can perhaps best see this in real time
where we see the echogenic foci here within the fluid
and posteriorly the reverberation artifact or comet tail.

Another type of nodule that doesn't come
to fine needle aspiration is the nodule that's predominantly
cystic but has multiple thin, internal septations.

It has the appearance much like a sponge
with fluid filled areas and then septations
or solid material between the areas of fluid.

And this indicates a benign non neoplastic nodule
in our experience even when the
septations are somewhat thicker, more heterogeneous,
more prominent, and also even when
the nodule contains these echogenic foci
within the fluid filled areas.

As we mentioned previously, sometimes there are
so many septations that it almost looks like a solid mass
with microcalcifications,
but if one looks carefully, we can see
that these echogenic foci lie posteriorly
within these fluid-filled areas
and giving the come tail artifacts.

This is perhaps best seen on real time images.

This is a benign nodule on your left,
a malignant nodule on the right,

the benign nodule on the left in real time.

You can see the fluid,
you can see the echogenic foci lying dependently in these
fluid filled areas and the comet tails behind them,

whereas the malignant papillary cancer on the right
is completely solid.

These echogenic foci are in the solid areas.

There's some faint shadowing behind some of the areas.

So what could look initially as similar types of nodules?

If one looks more carefully,
the nodule on the left has a benign appearance
nodule on the right, an appearance worrisome for malignancy.

Our suggested sonographic
or dictation when we encounter either a cyst
or a sponge-like nodule is to say
that this appearance is classic for a benign lesion such
as a cod or a colloid or non neoplastic nodule.

And of course, FNA is not recommended.

Another type of nodule that rarely comes
to find needle aspiration in our
practice is the larger cystic nodule.

Even if it contains more prominent internal septations
or debris within it, this is going to highly likely
represent a benign non neoplastic nodule even if it contains
large amounts of internal debris
or thick internal septations.

That is because these are not simple cysts, these tend
to represent hyperplastic nodules.

And these are the results of cycles of hyperplasia
and involution of the thyroid parenchyma,
which results in fluid filled areas
and some compressed solid material within
the thyroid nodule.

So a similar gross photo
of a benign hyperplastic nodule
and a thyroid fluid-filled area surrounding some
compressed thyroid tissue.

So the question would arise, could this represent
a cystic malignancy?

And the answer is it's possible,
but it is unlikely papillary cancer can
contain cystic components.

It's uncommon when it does
and these are visible, visible sonographic.

They generally tend to be small components in the periphery
of of the lesion In this particular case, if
that cystic area is larger,
we can see the large amounts of fluid.

And here there's a solid mass protruding into the central
portion of the fluid seen also on a similar
gross specimen.

And an additional finding if we look closely is there are
also micro calcifications within this solid component.

These are four additional predominantly cystic
papillary cancers.

We can see their large cystic components if we look more
carefully at the solid element.

We also do see these microcalcifications
located in each of these solid masses.

That's not present in every case of cystic papillary cancer,
but it may be present in many of the cases.

Also, it looks like this is a common lesion.

It's really not that common,
but these are four examples of papillary cancers
that are predominantly cystic.

The way to approach this though is to say that
as a practical perspective,
the predominantly cystic nodule has an extremely high
probability to be benign
because benign nodules are common,
often have a large cystic component.

Malignant nodules are rare
and rarely undergo large cystic change.

And even when they do have large areas of fluid,
additional findings of malignancies such
as the microcalcifications are often present.

Our suggested dictation when we encounter a nodule
that is predominantly cystic such as this is
that we say the appearance is highly likely
to be a benign lesion.

One final appearance that does not come
to find needle aspiration in our practice is the thyroid
that has multiple tiny hypo coic nodules within it.

And this almost certainly indicates Hashimoto's thyroiditis.

One can have this predominantly micro nodulation appearance
of multiple hypoechoic areas within it,
or larger hypoechoic regions separated
by prominent septations.

This is a very common disease.

In fact, it's the most common cause
of hypothyroidism in late stages of the disease
usually occurs in, women has a prevalence
of 4% of women.

It's an autoimmune disease where antibodies develop
to thyroglobulin grossly the,
gland and microscopically will show these small lobules
of lymphocytes separated by these fibrous areas.

And that accounts for the appearance
that we see sono graphically.

So here we have a gland with Hashimoto's on top,
a normal thyroid gland below for comparison.

You can see that with the Hashimoto's there's often diffuse
enlargement of the thyroid,
either multiple small hypoechoic nodules
or these hypoechoic areas separated
by the septations and bands.

And we can perhaps more clearly see this on real time
where we can see these hyper coic linear areas extending
through this more hypoechoic, regions of the thyroid.

If one uses color
or power doppler,
there's often increased flow within the gland,
particularly in the acute phase or
or active phase of the disease.

But that doesn't have to be present.

There can be normal or even decreased flow in Hashimoto's.

We also may see the predominantly micro nodulation
appearance on real time.

You can see the multiple hypoechoic areas
where these lymphocytes are
are present giving the hypoechoic nodules.

This is a very important pattern
to recognize sono graphically
because it has a positive predictive value of 95%
for Hashimoto's.

And also in one study it was interesting that three quarters
of the patient had patients had no known diagnosis of this
before the ultrasound exam.

So important to recognize this appearance.

So when we encounter a gland with this appearance,
we say there are multiple
or when there are multiple hypo coic nodules in both lobes,
we say that that appearance is typical
of Hashimoto's thyroiditis.

Parathyroid Glands in Primary Hyperparathyroidism

Well, let's now shift gears
and move from the thyroid to another gland
that is located immediately adjacent to the thyroid
and that's the parathyroid we'll concentrate on patients
with primary hyperparathyroidism.

This has an incidence of one per thousand in the population,
often in postmenopausal women
and 90% of the time caused by a single parathyroid adenoma.

To localize these enlarged glands in patients
with known primary hyperthyroidism, we need to understand
where the glands are located.

In the typical individual, the superior gland,
a patient will have four glands,
two superior and two inferior.

The superior glands are situated behind the mid portion
of the thyroid or array about this location.

The inferior glands are situated at the coddle tip
of the lower pole of the thyroid array about that location
or trailing off into the soft tissues of the low neck.

So behind the mid portion of the is where we look
for the superior gland behi.

Adjacent to the coddle tip for the inferior gland,

we don't see the normal glands in most individuals.

We do see them when they're enlarged in patients
with hyper parathyroidism.

So the typical superior parathyroid adenoma on the
longitudinal view is an oval hypoechoic,
bean shaped mass situated behind the
mid portion of the thyroid.

And on the transverse view, it's located
between the common carotid artery
and trachea in the triangle made by the trachea thyroid
and common carotid artery.

The typical inferior parathyroid,
gland on the longitudinal view is located just coddle
to the thyroid itself.

And on the transverse view,
because we're coddled to the thyroid, it's located
between the trachea and the common carotid artery
and it tends to be somewhat in a plain more anteriorly
than the superior adenomas,
which lie in a slightly more posterior plane.

The typical adenomas are, as you've seen here,
a bean shaped hypo hypoechoic mass.

But there can also be a spectrum of appearances
that can be quite small,
just a few hundred milligrams in size to others
that are very large, several grams in size,

they're usually hypoechoic.

Occasionally they can have large amounts of fat within them.

The rare fatty lipo adenoma
or uncommonly, they can have large cystic components
in all four of these cases.

These patients were cured when these,
adenomas were removed.

So there can be a spectrum of appearances,
although these other appearances are less common.

We can also use color
or power doppler imaging to evaluate these adenomas.

We can see there's large amounts of flow.

They generally tend to have a feeding artery at one
pole of the adenoma.

As we see here on the real time clip.

It enters through one end
and then supplies the vascularity throughout the adenoma.

Usually this is a branch of the inferior thyroid, a artery
that supplies the parathyroid adenoma.

It could be from the superior thyroid artery.

It's helpful in terms
of differentiating this from other types of similar masses.

Thyroid nodules can be hypervascular,
but they tend to have multiple vascular channels entering
from multiple different locations.

Lymph nodes have a single entering vessel,
but it tends to be a low amount of flow
and enters into the central portion of the lymph node
and then branches in a regular pattern within a normal lymph
node as opposed to the parathyroid adenoma where it enters
through one of the poles.

Multiple gland enlargement can occur as well in five to 10%
of cases of primary hyperparathyroidism.

This can be asymmetric enlargement of the gland.

Here at glands here we see all four enlarge,
but one may see three
or two glands enlarge due to the asymmetry.

It's just important to let the surgeon know
that there may be more than one parathyroid gland enlarge
so they can explore all of the potential locations
for the parathyroid adenomas or parathyroid enlargement.

Parathyroid cancer can also occur. This is quite uncommon.

It accounts for only one in 200 cases that present
of individuals with hyper parathyroidism.

A clue is sometimes that the calcium
and paraform levels are markedly elevated more than would be
expected, But usually the diagnosis is made at the time
of surgery when the surgeon encounters a mass,
which is firmly fixed
to the surrounding tissues at operation.

We can see that here with the lobulated contour of this mass
extending and interdigitating into the tissues around it.

So this was a parathyroid cancer,
but most of the time it, the masses just appear as a large
but otherwise normal appearing in large parathyroid gland
and the diagnosis is made at surgery.

Ectopic Parathyroid Adenomas

Most of the parathyroid adenomas are going to lie in typical
locations, but about 2% can be frankly ectopic.

And we'll look at the pattern that the surgeon employs
to try to find these glands that may be
mediastinal retro tracheal, intra thyroid
or laterally in the carotid sheath
or unds descended location.

When an inferior gland is ectopic,
it has generally continued its embryologic descent along
with the thymus into the anterior superior mediastinum.

The surgeon, if they don't find the gland in the normal
location, will then start to tease up the fatty tissue
behind the sternum to look for these adenomas.

We can do the same by angling behind the sternum
and we may see a bean shaped mass within the more hyper coic
tissues in the anterior mediastinum, the same adenoma,
even though it's located directly behind the bone
by angling coddly, we can often see these sono graphically.

The superior glands when they are ectopic tend to
continue their embryologic travels into the posterior aspect
of the neck or posterior superior mediastinum.

If the surgeon doesn't find it more anteriorly, they tend
to run their finger behind the trachea and
and probing more deeply into the low neck.

In attempt to find these glands
here we can see the same adenoma on ultrasound and ct.

If we angle through the thyroid gland,
we can often see these large masses here, this one located
adjacent to the cervical spine
and they tend to be missed sometimes at initial operation
'cause the surgeon may be reluctant to
explore deeply in the neck because of nerves
and other important structures.

And these may, be present when we look at these patients
for reoperation, for persistent hyperparathyroidism.

Another place that the,
adenoma may lie is in a completely intra thyroid
location here on the transverse
and longitudinal view completely surrounded
by thyroid tissue.

They're very homogeneous
and hypoechoic have the same type of appearance
of a parathyroid adenoma
that one would see elsewhere in the neck,
but this tends to be completely
surrounded by thyroid tissue.

If we look with color doppler imaging,
they are quite vascular as we see here.

And if we're fortunate, we may see the feeding artery where
that has been pulled into the thyroid parenchyma along,
with the parathyroid adenoma, the surgeons look for these,
they tend to be quite soft though they're difficult
for the surgeon to palpate.

Fortunately, they show, quite nicely
sono graphically from the remainder
of the thyroid parenchyma.

Finally, these
parathyroid adenomas may lie laterally in the neck.

It's unclear how they
become in this location embryologically,
but they can be within a sheath of tissue
that surrounds the common carotid artery,
internal jugular vein and vagus nerve, the carotid sheath.

And the surgeon needs to open this sheath
and then look inside to see if they can see a mass such
as this situated between the jugular vein
and carotid artery.

This patient also had a nuclear medicine scan
that showed this activity in this place laterally in the
neck, and the patient had had
previous operations in an attempt to identify this, so,
certainly wanted even more information
before having an additional operation.

So with confirmation, fine needle aspiration was performed
where a needle was inserted into the nodule,
avoiding the vessels
and obtaining material

On these aspiration biopsies
of parathyroid suspected parathyroids.

The they can be analyzed in three ways.

One, the material can be sent for cytologic analysis
with a small caliber needle if the nodule in question
is adjacent to the thyroid.

Some have used cutting needles
because the pathologists prefer a larger sample
to distinguish the parenchymal parathyroid cells from the
parenchymal thyroid cells
and they have difficulty on cytology alone.

But perhaps the best, best method
and the one that is in most wide use now is
to send the material for parathyroid hormone analysis.

This is, called a washout technique or
after the small caliber needle such
as the 25 gauge needle has been inserted into the mass
it's washed with saline that's repeated several times.

So at the end of this procedure, you have about a half cc
of blood tinged fluid within a standard test tube
and that material is sent to the lab.

If the parathyroid hormone levels are markedly elevated,
then that should represent parathyroid tissue.

If they're at baseline with the blood
or very low, then it should not represent parathyroid
and this has proved to be more sensitive
and more specific than the cytology or histology.

And if one uses these techniques,
we've talked about a knowledge of the typical adenoma
locations, a systematic scanning approach of the normal
and the ectopic locations, and also using color doppler
and even fine needle aspiration as needed.

Then adenoma detection can be quite high using ultrasound.

Other Localization Methods and Minimally Invasive Surgery

There are certainly other methods
of parathyroid adenoma localization, sestamibi scanning,
particularly using I 1 23
or SPECT imaging is, very accurate
and has supplanted ultrasound in some practices.

Also CT using aphasic technique
with a rapid bolus of contrast.

Here we can see an enhancing adenoma deeply in the neck
adjacent to the esophagus
and we tend to use these techniques as well.

But we often start in our practice with sonography
and if that's inconclusive, use these other techniques
as well, particularly tib scanning.

One change in the treatment of patients
with parathyroid adenoma that has occurred in the,
recently is the transition from the traditional type
of operation to the minimally invasive type of operation
to remove these parathyroid adenomas.

There are certainly advantages to this.

The traditional operation has a larger scar
with the minimally invasive operation.

It's a smaller scar, less pain,
and the patient spends less time in the hospital.

So there are certainly many reasons to prefer this.

If it's possible to perform
the minimally invasive operation,
it does require excellent preoperative localization.

Here on both ultrasound
and scintigraphy, we've confirmed there is a hyper
functioning nodule consistent
with a parathyroid adenoma in this location in the neck.

So the patient or the surgeon knows where
to make the incision, the small incision
to remove this adenoma.

So the precise localization is needed.

One also needs intraoperative parathyroid
hormone monitoring.

As soon as this is removed at operation,
the paraform levels are measured.

If they've dropped, rapidly
and significantly, then the surgeon assumes that
that is all of the tissue that is present and closes.

If the epithermal remains elevated, then they can convert
to a traditional operation,
explore other regions in the neck,
and make sure there's not other hyper functioning
parathyroid tissue in the neck.

Conclusion

So in conclusion, we've looked at both thyroid
and parathyroid imaging.

We've seen that ultrasound is a powerful tool for evaluation
of these types of masses,
and I hope that this will be useful in your practice.

Thank you very much.