Ultrasonography of Superficial Soft Tissue Masses - SD

Introduction

Hi, I am Lev Nazarian.

I am professor of radiology at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania.

I will be speaking on ultrasonography of superficial soft tissue masses.

Importance of Imaging Superficial Soft Tissue Masses

The importance of imaging superficial soft tissue masses is illustrated by this case where a biceps tendon rupture was suspected by the orthopedic surgeon.

But in looking at this image, one sees that where there was thought to be a hematoma from a biceps rupture, in fact, there is a mass involving the biceps muscle.

Now this could be a hematoma from a biceps rupture, but it's important to use all the tools at our disposal when we're evaluating a soft tissue mass.

And we realized that when we put the color Doppler imaging on this mass, that it has neovascular within it.

Therefore, what was suspected to be a biceps tendon rupture really ended up being a sarcoma involving the biceps muscle.

So anybody who is performing musculoskeletal ultrasound needs to be aware that not just traumatic pathologies, but sometimes tumors may occur in their patient and that they need to have a framework by which to evaluate palpable soft tissue masses.

General Approach to a Suspected Soft Tissue Mass

The general approach to a suspected soft tissue mass is first to take a thorough history, because often the history will dictate what type of pathology you're expecting to see.

If the lesion is palpable, have the patient point to the area of interest.

If the patient does not have a palpable mass, then consult correlative imaging.

It may be that a mass was seen on CT MRI, et cetera, and needed an ultrasound to evaluate it further.

And if you have these other images available, it is good to consult them.

It's also helpful to know whether the mass is painful or asymptomatic or whether it's been stable or growing because all of these may help in your differential.

It is also important to know potentially pertinent medical history.

Does the patient have a prior history of malignancy or trauma?

Have they had surgery? Are they on anticoagulation or do they have any systemic diseases that could be pertinent?

Ultrasound Technique for Evaluating Superficial Soft Tissue Masses

Now the ultrasound technique that one uses in evaluating a superficial soft tissue mass is to minimize the depth of the lesion to include the mass and place the focal zone at the level of the lesion.

Then after you identify the lesion, you want to assess the vascularity in and around the lesion by color doppler to evaluate the blood flow.

Power doppler, which can be somewhat more sensitive than color doppler, and then spectral doppler to confirm the presence of arterial and or venous flow in the lesion.

You also then want to measure the size of the lesion in three dimensions and you want to characterize its echogenicity, is it hypoechoic, iso coic, hyper coic or mixed?

And usually these terms are relative.

So one needs to have a standard of reference and usually we use muscle as the standard of reference when we're characterizing the echogenicity of a mass.

Next thing are to characterize its borders.

Is it well-defined or does it blend in with surrounding tissues?

And what does it do to the ultrasound beam?

Does it cause acoustic enhancement or does it create acoustic shadowing?

Next thing is it's important to localize the mass to a compartment because again, depending on the compartment, a different differential will present itself.

So the mass could be in the skin, it could be in the subcutaneous tissues, could be in the muscle, could be related to a joint or a bursa or other musculoskeletal structure.

Understanding Normal Architecture of Soft Tissues

In order to be able to localize masses to compartments, it's important to first understand the normal architecture of the soft tissues.

On ultrasound, when looking with the high frequency linear probe, the first layer that one will see superficially is the dermis of the skin.

Then we have the subcutaneous fat layer, which is variable thickness depending on the patient and depending on the part of the body, it's important to recognize that this fat layer may be hypoechoic, but often is hypoechoic because in fact pure fat is hypoechoic on ultrasound.

And do not mistake this for fluid or some other pathology.

This is the subcutaneous fat, the normal appearance.

Often then there will be a bright fascial plane that separates the subcutaneous fat from the underlying muscle.

And the muscle is seen here with its characteristic penate pattern that one sees in muscles with little bright fibroadipose septa that are separating hypoechoic muscle bundles.

Lipomas

So the lipoma, the most common mass that we encounter in our practice ranges from hypoechoic to iso coic to hypoechoic.

And that is because although I alluded to the fact that pure fat is hypoechoic, in fact, depending on what other tissues are mixed with the fat, for example, fibrous tissue or connective tissue, a lipoma may have a wide range of appearances.

You may even see internal septations within a lipoma and that's a very characteristic appearance.

One thing about lipomas is that they're difficult to separate from the adjacent fat and that's because they also are fat.

And so paradoxically, if you see a mass that has ill-defined borders that kind of blend in with the surrounding tissues, one is more likely to think of a benign process such as the lipoma because it is inseparable from the fat that surrounds it in certain cases.

Now, some examples here is a lipoma that's slightly hyper coic to its adjacent fat.

Here's the lipoma here, it was palpable.

Here's the underlying muscle.

It's about iso coic to the underlying muscle and you can see why it's palpable because it does deform slightly the tissues around it.

Now here is another example of a lipoma where I'm first gonna show you the normal tissues and then as we swept the probe along where the palpable abnormality was, we saw this very subtle nodule that was blending in with the surrounding fat.

Again, one might think, ill-defined borders must not be a good thing, but in this case, the fact that we have fat adjacent to fat accounts for the fact that the borders are difficult to see.

So that actually is one of the hallmarks of a lipoma when it blends in with the surrounding tissues.

And there it is there.

The other characteristic of lipomas on color doppler is that they tend to have little or no flow.

The important part of evaluating a lipoma is always to remember to put on the color doppler to make sure that there is no neovascular or anything that might sway you into thinking that it is anything but a lipoma as this one had no flow in it.

Bilateral comparison can be helpful too if you're not sure if you're looking at a normal location or fat or an actual lipoma.

This bilateral comparison shows the lipoma on this side deforming the underlying fascia where on the other side you just have the skin subcutaneous fat and muscle and that extra layer, which is the lipoma, is missing on the left side so it can be more confident in your diagnosis.

Extended field of view is useful extended field of view technology can give you a more panoramic image of an area and can give you a better feel for how big a lesion is.

And this comes into play quite often in lipomas 'cause they can become quite huge and will not be able to be imaged completely on one ultrasound image.

And the problem with that is twofold.

First of all, it's difficult to document the entire lesion, but also it's difficult to measure it if you'd use extended field of view imaging, you can get measurements and actually then you can use those measurements to report the size and also to use as a baseline for follow up.

Here's another example of a lipoma that has sort of mixed genicity within it.

There's some hypoechoic areas, some hypoechoic areas within it.

And extended field of view really helps you delineate it better because it's a very huge mass that's involving the quadriceps muscles.

It's about 15 centimeters in length, or even more.

And it's something that you will not be able to appreciate all on one image.

The reason I know this is a lipoma is that by patient history it had been stable for about 15 years, but certainly a lesion this big, you'd have to put low grade lipo sarcoma in your diagnosis, especially if there were a history of recent growth.

This is another characteristic appearance of lipomas, these preserved septa that one can see within the mass.

Now this patient had had a history of melanoma and was being sent for a new palpable mass.

So I wasn't completely comfortable at this point of letting this go.

And so I wanted to get correlated imaging to prove that this was in fact a lipoma.

Here's the MRI showing the lesion, which actually tracked with fat on all pulse sequences indicating that in fact it was a benign lipoma.

Liposarcoma

Okay, now here's an example of a lipo sarcoma, a low grade lipos sarcoma.

And at first glance this looks exactly like the lipomas I've shown you it, its margins kind of blur with the surrounding fat.

It has some septations within it and it has areas of hypo and hyper coic tissue.

So one might think, okay, that's fine.

But there were two problems about this that made me worry about it.

Number one is that the patient said it had recently been growing very rapidly.

And the second thing is that when we put the color doppler on, we saw vessels kind of irregular vessels within the lipoma, which made us think more that it was a lipo sarcoma, which is what it turned out to be.

So you may see a dot or two of flow in a lipoma, but if you, certainly, if you see this sort of neovascular within it, you really have to think that you may be dealing with a low grade lipo sarcoma.

And that's why ultrasound is not perfect in differentiating lipomas from other lesions.

Doppler can be helpful in that regard.

Whenever you do a doppler, it's always good to put on the spectral to prove that you're not just seeing noise within the lesion.

This is an arterial waveform documenting that there is arterial flow within this lipos sarcoma.

Determining Cystic vs. Solid Masses

Now much of what we are asked to do under ultrasound is to determine whether a mass is cystic or solid.

And although this sounds straightforward, it can be tricky sometimes to make this differentiation.

The first thing we go for is by the gray scale appearance, but in other words, cystic lesions tend to be relatively without echoes and solid masses tend to have echoes within them.

But note that cystic masses can have echoes within them and solid ones can be relatively hypo or an coic.

The important thing to understand about the soft tissues is that acoustic enhancement does not mean the mass is cystic.

And I'll go into that in more detail in a little bit.

The next thing is does the mass change with compression?

Because cystic masses, if you can demonstrate that it changes with compression shows that there is a fluid component to the mass.

The next thing is the presence of internal doppler flow.

Internal doppler flow is more helpful if it's present than if it's absent because if flow is present it excludes that the mass is a fluid collection.

Of course, if doppler is absent, it still may be solid and hypovascular.

So again, flow is more helpful if present than if absent.

Examples of Fluid Collections

Okay, now some cases, here's an example of a fluid collection.

This patient had a resection of inguinal lymph nodes for metastatic melanoma and presented with a recurrent mass in the inguinal region.

Scanning shows virtually no echoes within this lesion there is through transmission, but as I told you before, that is not a useful sign which I'll explain to you in a moment.

We did put on the doppler, did not show flow within it, but again as absence of flow is not as helpful as presence of flow within the mass.

So we felt with the history of melanoma, we were obligated to at least stick a needle in this and send it for cytology and we were able to drain this out completely.

Cytology was negative and this was a postoperative seroma in the inguinal region.

Here's an example of how compression can give you an etiology of a lesion.

This patient presented with a mass in the inguinal region and this was the mass without compression and here was the mass with compression.

You can see that the marked change in the shape of the mass indicates that this is a fluid containing mass.

And if you look more carefully, you actually see that this patient had a failed femoral graft and that is an abscess that has formed around this failed graft.

You can see the internal echos within this abscess and we drained it out and we got puss from this.

But again, doing compression proves that it is in fact a fluid containing structure.

Acoustic Enhancement in Superficial Soft Tissues

This is an example that I show to hit home the fact that acoustic fluid transmission is not helpful in the superficial soft tissues to tell you if a mass is cystic or solid.

This patient had a history of melanoma and presented with a recurrent palpable mass in the subcutaneous tissues.

Here is the mass, it has some low level echoes within it, but it has an incredibly nice burst of through transmission behind it.

But I will tell you that this was a proven metastatic melanoma.

It simply is not a helpful sign.

In fact, when we studied the ultrasound appearance of melanomas, we published a series in which 72% of metastatic melanomas and the soft tissues had increased acoustic through transmission.

It is simply an unhelpful sign.

This this example I show to illustrate that solid lesions may have little or no echoes within them.

This is another melanoma patient who presented with a mass in the lower back and we see this irregularly shaped mass.

Now, we initially thought it was a fluid collection, but then we put on the doppler and there was internal arterial flow within this lesion and it is a proven melanoma metastasis by biopsy.

The key thing here to understand is that if a mass is very homogeneous, let's say for example you have a very homogeneous population of lymphoma cells or melanoma cells, there will be very few acoustic interfaces and so the mass may be almost completely echo free as it was in this case.

Ultrasound-Guided Biopsy

Ultrasound guided biopsy is very important in the armamentarium of the sonographer or sonologist because the gray scale and color doppler characteristics are often non-specific.

And so when in doubt percutaneous biopsy should be used and it is a very safe and effective method for diagnosis.

Here's an example of a very non-specific lesion that biopsy was needed to make a diagnosis.

This is a patient who presented with a mass on the thigh.

We put the ultrasound down and we saw this lobulated mass.

It looked somewhat solid, it did have acoustic through transmission, but again, not a helpful sign in the subcutaneous tissues.

There was a lot of hyper coic fat around it, so it looked like the body was reacting to it, but we really didn't know what it was.

We put on the color doppler and there was a lot of vascularity within it.

In fact, putting the power doppler on which is somewhat more sensitive really showed a lot of irregular vessels.

Now, benign lesions can have vessels within them too, but whenever we see vessels in a benign lesion, they tend to have a more homogeneous and monotonous branching pattern.

These vessels are very squiggly.

They kind of come and go from nowhere and really have what we associate with a malignant process.

But there's nothing about this mass we can say further except that it's solid and that it needs to be biopsied.

Here's a needle within the mass and this happened to be a presentation of lymphoma in the soft tissues, the patient's first presentation of lymphoma.

Again, no way to make that diagnosis, but the fact that we can so easily and safely do a needle biopsy with ultrasound guidance improves upon our simply gray scale appearances to be able to perform interventions to make the diagnosis.

The Real Estate Approach: Location, Location, Location

Now the next section I call the real estate approach to soft tissue masses, location, location, and location.

It's important in real estate and it's important in superficial soft tissue masses because sometimes the place that a lesion occurs is so characteristic that you know what it is just by where it's, for example, the baker cyst.

Baker cysts are distended bursa that occur between the medial head of the gastrocnemius and the semimembranosus tendon at the medial posterior aspect of the knee in the popliteal fossa.

So this was a patient who came in for rule out baker cyst and in fact there was a baker cyst in the characteristic location.

There is nothing else you need to do.

This is absolutely a baker cyst.

Can't be anything else because of its characteristic shape and appearance.

The problem was that the same patient had a palpable nodule in the lateral aspect of the knee and it's very important to recognize that baker cyst do not occur laterally in the popliteal fossa.

They occur immediately so by location already we were worried that this was something else and in fact it did have some blood flow within it.

In speaking with the patient, she had a history of lymphoma.

She was thought to be free of disease, but this was a recurrent lymphoma and the popliteal area at this lesion was positive on a subsequent PET scan.

Here's another mass that is so characteristic in location you don't need to do anything else.

This patient presented with a mass in the neck and was actually sent for me to biopsy it.

This is the external and internal carotid artery that are splayed by this mass.

Okay, so by the location we were suspicious that it was a carotid body tumor.

We then put on the color doppler and the color doppler showed the characteristic abundant flow within an carotid body tumor.

And so there was no way that we would be biopsying this.

The characteristic location and the blood flow made the diagnosis and we don't need to put in a needle to confirm it.

Another characteristic location.

This is a 16-year-old with a soccer injury who presented with a palpable mass over the thigh and this mass was a lenticular fluid collection with a lot of inflamed hyper coic fat around it.

And this happens to be a characteristic location for what is called a morel lavallee lesion, our so-called internal degloving injury.

We were able to aspirate this fluid for symptomatic relief, but the fact that it was in such a characteristic location really gave us no differential diagnosis.

And there it is with the needle in place having aspirated the fluid out.

Another characteristic location of a mass is the glomus tumor in the finger.

This is a patient who had had a glomus tumor, which is a vascular tumor, very painful, often under the nail bed in the finger, and it had been resected, but the pain came back and the question was, did the glomus tumor come back?

Well, we scanned under the nail bed and we saw abundant tufts of flow here with arterial waveform on spectral analysis again by location.

This was a recurrent glomus tumor and this was proven at surgery.

Vascular Masses

Now, there are a number of vascular masses that ultrasound can really contribute to their evaluation and when you're looking at a mass that you may think may be a hemangioma or some other type of vascular mass, there are several things that ultrasound can help you with.

Number one is you wanted to get some idea of the amount of flow, the type of flow.

Is it arterial and or venous?

The distribution, is it central and or peripheral?

You always wanna use power doppler for increased sensitivity and spectral doppler to confirm that you're not just looking at noise, but it's really true flow within the lesion and to tell whether it's arterial or venous.

Here's an example of an MRI, which showed on T one enhanced images an enhancing mass in the left lip.

But what this MRI does not tell you is exactly what type of flow is present within this presumed vascular lesion.

And that's where ultrasound is a very nice adjunct to MRI.

When we did an ultrasound of this lesion, we found that they were dilated vascular spaces with bright echoes interspersed, which were consistent with phleboliths.

When we actually did a doppler of this lesion, we found no arterial flow, only venous flow, so this was characteristic of a venous malformation and that gives an added extra bit of information to the surgeon to know what they're gonna be expecting when they go into treat this lesion.

And here is the doppler of that flow showing just a venous waveform.

No arterial flow was detectable throughout this lesion.

Now in contradistinction, here's another lesion which was present in the region of the left masseter muscle and this again is a T one weighted gadolinium enhanced image, which shows a hyper enhancing lesion in the left masseter muscle.

But again, the surgeon wants to know what kind of vascularity should I be expecting here?

So then we did a doppler of this lesion, which showed abundant flow within it, and this was our arterial flow on spectral doppler analysis.

So again, the surgeon was able to know that this in fact was a hemangioma and it was known that when they went in for surgery, they had to be careful because of all the degree of arterial flow.

This was a higher risk of bleeding, certainly a higher risk of bleeding than the venous malformation that we just showed.

Here's a woman who had a palpable mass that was only intermittent in the chest wall and we had her create the mass which she was able to create by increasing her intrathoracic pressure.

And when she did that, this mass popped out and it looked like a cyst.

And of course patient says, well, can you drain this for me and make it go away?

Well never do anything like that until you put on the doppler.

If you put on the doppler in this patient, you notice that there is arteries and this is a vein which has popped out.

It actually turned out to be the internal thoracic or internal mammary vein, the synonyms.

And this vein popped out when she increased her intrathoracic pressure.

And here's the internal mammary artery tortuous beneath it.

So certainly a very important tool to have is doppler because you certainly don't want to be draining this with a needle.

Again, location and doppler help you figure out what this lesion is.

This is a patient who sustained a gunshot wound to the groin and presented with a palpable mass, which was pulsatile.

This is the superficial femoral artery and leading from the artery is this doppler track that leads into a hematoma.

When we image the neck of this track, we see the typical two and fro wave form that is characteristic of the neck of a pseudo aneurysm.

So this what subsequently went on to ultrasound guided percutaneous thrombin therapy to close this pseudo aneurysm.

Lymph Nodes: Benign vs. Malignant

Okay, now a lot of what we see when we're imaging the musculoskeletal system or soft tissues or lymph nodes.

And so it's important to understand a framework on how to determine benign for malignant lymph nodes.

So what are benign features of lymph nodes?

First of all, an oval shape and that was defined by solti as a length to AP ratio of greater than two.

The second thing you wanna see is a preserved echogenic hilum.

The third thing of a benign node is homogeneous echo texture and it should have a regular Doppler flow pattern of nice regular branching of vessels.

Here's a prototypical normal lymph node.

Again, it's oval, it's got a preserved echogenic hilum, it's homogeneous and echo texture.

This is by contradistinction, an abnormal lymph node.

This is a patient who had an anal carcinoma, which shows that it is rounded rather than oval.

The echogenic hilum is obliterated, the mass is very heterogeneous and this was a proven lymph node metastasis.

I also want to give just that in case I've already not made the point that there was a lot of good through transmission through this metastatic lesion.

Again, not helpful in these superficial tissues.

Here's another metastatic lymph node from melanoma.

A metastatic inguinal lymph node, again rounded rather than oval, very heterogeneous, no echogenic hilum.

It had increased flow on color Doppler not shown here in sort of an irregular pattern.

Now this lymph node was treated and this was a follow-up study showing that the benign characteristics of the lymph node had returned.

The echogenic hilum had returned, it was now oval again.

And because the patient was part of a protocol, this was resected and there was only necrotic tumor at the periphery, no viable tumor.

So basically this shows a malignant node and then return to more benign features after treatment.

Lymph nodes may also be malignant because of their behavior.

This is an ultrasound of the left side of the neck, which shows a mass, which does not have any benign characteristics of a lymph node.

But the other signal that this is in fact malignant is the fact that it is causing thrombosis of the adjacent internal jugular vein.

And this turned out to be metastatic breast carcinoma to the neck.

This is a patient with a history of carcinoma of the thyroid and had a palpable mass.

And when we looked carefully, we realized we could see the common carotid artery on the right, but that the internal jugular vein was completely filled with echogenic soft tissue.

So again, a malignant node not only by its morphology but by its behavior invading the adjacent vein.

Now, normal lymph nodes I told you before, have sort of a monotonous flow pattern and so on doppler, we will see vessels coming into the hilum and monotonously branching within the lymph node.

And here it is on power doppler.

Now here's a malignant lymph node again, rather than a vessel coming in at the hilum and branching homogeneously, we have irregular vessels all through this lesion.

Some of them are at the periphery, some of them are more hilar, echogenic hilum is gone of course, but we see this very, very irregular flow and this was a melanoma metastasis.

Periarticular Processes Presenting as Soft Tissue Masses

Now there are a number of periarticular processes that can present as soft tissue masses, and so we have to be cognizant of those bursitis.

Ganglion cysts can occur.

I've already shown you one baker cyst.

Again, here's another, and again, a very common cause of a palpable mass behind the knee.

And again, we always wanna look for the gastrocnemius and semimembranosus with the bursa coming up like a mushroom in between iliopsoas bursitis can also be palpable and present as a mass.

Here's the common femoral artery and vein and there's a mass next to it and somebody who's not aware of the presence of this bursa could call it a metastatic lymph node or some other abnormal lymph node in the left inguinal region.

But if you follow this down, you realize that it tracks along the iliopsoas tendon, which is this bright area here.

And then as the tendon attaches on the lesser trochanter, this lesion goes away.

And here on ultrasound is an example of a distended iliopsoas bursa.

Again, they live behind the common femoral artery and vein and the way you'll know that it's a bursa is that it'll abruptly end right at the lesser trochanter.

It'll have fluid and debris in it and they can get quite large.

They can actually grow up into the pelvis and often they will be associated with hip pathology either because of arthritis or because the patient has had a hip replacement in the past.

Here's another example of an iliopsoas bursa.

They can be filled with very thick material such as in this case again, here are the vessels for comparison.

And this particular bursa you can see extending up into the true pelvis with only a small amount actually fluid, the rest of it being very thick debris.

This is probably the biggest one I've seen where here's the iliopsoas tendon with a very, very thick, huge bursa with a extended field of view.

Here is the acetabulum and femoral head and it went all the way from the lesser trochanter all the way up over the acetabulum and into the pelvis.

Again, they can become quite large and you have to think about it whenever there's a palpable mass in the inguinal region.

Ganglion cysts can occur anywhere.

They're very common in the hands and feet, but can occur anywhere in association with joints or tendon sheets.

And this is one area that's very common, a volar part of the wrist ganglion cyst.

And the key thing about this is that it may lift up the radial artery shown here, and this can present as a pulsatile mass.

So it's important when you see something that you suspect to be a ganglion cyst put on the doppler.

And in fact, you see there's no flow within the ganglion, but there is flow in the overlying radial artery.

And you could see why clinically this could mimic a pseudo aneurysm since the artery is so easily palpable.

Muscle-Related Masses

All right.

Now muscles can present as masses.

You can have traumatic rupture or herniation of the muscle.

You can have hematomas, you can have abscesses, you can have myositis specific hand or neoplasms.

Here's an example of an acute hemorrhage.

Somebody was lifting grocery bags and felt a tear.

And in the left rectus abdominis, here's the right rectus abdominis.

In the left there was a big hematoma in the rectus sheath.

Here's a CT showing some layering of acute blood within this left rectus hematoma.

Again, compare it to the normal right side for comparison.

This is a patient who was sent for rule out sarcoma and pointed to a non-tender mass on the thigh.

At first glance, this mass looked like a muscle tear, but the patient was not giving such a history.

But on further questioning, patient asked if it could have something to do with the fact that he fell off a bus two weeks ago.

He had not initially told that to his physician.

The pain had gone away, but he was left with a palpable mass.

And this is the rectus femoris muscle showing a tear and then a hematoma around it.

Now this is a case which taught me a lot about imaging of muscles and also about imaging tumors in general.

This was a patient who had, his chief complaint was he had pulling in his quadriceps muscle when he contracted his leg.

These are the fibers of the rectus femoris muscle.

And they came out into this very amorphous, very poorly defined heterogeneous mass within the quadriceps muscle.

Now this could be the presentation of a primary sarcoma, but it turns out that the patient had history of melanoma taken out from the same extremity a couple years ago.

So we were very suspicious this could be a metastasis.

We then scanned around the knee looking for others and there were multiple implants within the subcutaneous tissues, all very similar looking, all very hypoechoic, which melanoma can be.

And we sent 'em off to surgery and these all turned out to be melanoma metastases that were not palpable.

So then we realized that ultrasound can be a very powerful tool and not only in diagnosing and guiding biopsy for soft tissue masses, but also in identifying non palpable masses in tumors such as melanoma.

Here's another non palpable mass in this patient, higher up in the thigh.

And so we then used ultrasound as a means to follow him.

He was clinically free of disease when he came in a few months later, but we did a survey of the lower extremity and we found this lesion, we put the doppler on it and it had very irregular flow.

So he was thought to be free of disease at this point, but in fact had a pretty good size metastasis in his upper thigh.

So when patients are at high risk for melanoma metastasis, if they have a very deep lesion, one that's high risk for spread, we have found that ultrasound is an excellent tool to identify melanoma metastases and then of course to guide biopsy if possible.

Other Types of Masses

Now, here is another type of mass which on first glance could look similar to something like a metastasis or some other malignancy.

But the morphology of this lesion is the clue to what it actually is.

This lesion has a nerve entering it and exiting it, and that shows that it is in fact a neurofibroma.

It could also be a schwannoma, but the bottom line is that it shows that it has a neural origin.

So whenever we see a superficial mass, it's important to look for whether a nerve is entering or exiting it because that can be a clue to its etiology.

Nerve tumors also can be quite tender and that can be helpful as well.

Here's a more extended field of view of this same lesion and showing, first of all the, the nerve coming into the lesion and exiting it, but also showing the doppler flow that can be seen in nerve tumors.

Finally, it's always important to remember that it's not always a soft tissue mass that's providing the palpable abnormality.

Here's somebody who presented with a palpable lesion in the neck and it was thought that there was some kind of lymphadenopathy or some other mass, but when we really correlated carefully the patient's symptoms with where the palpable abnormality was, we realized that what the patient was feeling was in fact bone.

We went and got a radiograph.

And when we mag up on this area, we saw that there was a pseudoarthrosis between the lateral elements of the cervical spine that was protruding out and causing the palpable abnormality.

So ultrasound, by being able to correlate the palpable abnormality with the ultrasound findings can detect not only soft tissue masses, but even bony prominences as well.

Foreign bodies are another lesion that can present as a mass, and this is a foreign body within the subcutaneous tissues.

And when we put on the ultrasound probe, we realized that we should mark the skin for the surgeon because it may be hard for them to find.

And this is an operative image showing the foreign body removed from the foot.

And you could see that the surgeon only had to make a very small incision because we were able to identify this foreign body as a cause of the patient's palpable lesion on the plantar aspect of the foot.

Conclusion

Okay, so in conclusion, ultrasound is useful in a differential diagnosis of a wide array of soft tissue masses.

Correlative imaging should always be used when necessary and when in doubt tissue diagnosis is necessary because often soft tissue masses are non-specific.

But I hope at least in this lecture that I've given you a framework when you're encountering a soft tissue mass in the soft tissues.

Okay?

So I hope that at least in this lecture I've given you a framework when you are presented with a patient with a palpable mass on how best to evaluate the mass to at least narrow the differential and to guide subsequent procedures, either diagnostic or therapeutic.