Ultrasound Imaging of the Salivary Glands - SD

Introduction

Hi, I am Dr. Ed Grant. I'm from the University of Southern California in Los Angeles, and I'm gonna be talking about ultrasound of salivary and peri salivary gland masses and biopsy techniques in that area.

I'm gonna be talking about ultrasound imaging of the salivary glands, and as I mentioned, we're gonna end this by bringing in a little bit about how we do biopsy techniques in this area and in the surrounding masses that may occur.

Ultrasound Imaging Techniques

For imaging. Of course, these are very superficial structures and therefore a very high resolution probe is essential. Gives you very, very good resolution. And of course, typically we use a linear array transducer. We also typically will involve power and color doppler to look for masses and inflammatory processes.

Normally, although the patient will typically present with a unilateral process, a bilateral examination is a good idea 'cause many of these things may be multifocal, inflammatory processes may be bilateral as well. It's also a good idea to scan somewhat lower in the neck for lymph nodes and in patients predominantly with submandibular disease. Looking for a thyroid primary may be important as well, in that it may rarely be metastatic to the submandibular gland area.

Remember also that, particularly the deep lobe of the parotid glands, lie behind the mandible and will often require CT and MR for adequate imaging.

Anatomy of the Major Salivary Glands

The major salivary glands are three, as is shown in this image. There's the parotid gland, there's the submandibular gland and the third one, the sublingual glands, which are small and located beneath the mandible. We'll discuss a little bit later. Excellent review article by Bialek et al in Radiographics from 2006 from which this image is taken.

Parotid Gland

The parotid gland is located in the retro mandibular fossa, again, immediately anterior to the ear and the sternocleido mastoid muscle. It covers the posterior mandible and the masseter muscle. The facial nerve is an important structure that divides the parotid gland into the superficial and deep lobe, but unfortunately is usually not visible with ultrasound. But we do use the adjacent retro mandibular vein and external carotid artery as adjacent landmarks to locate the nerve.

Normally the parotid gland is homogeneously echogenic, and the echogenicity is said to actually be proportional to the amount of fat within the gland. Benign int glandular nodes are quite common around the parotid and within it.

The normal parotid as is shown here, has a relatively homogeneous gray scale appearance. The masseter muscle may be seen, posterior to it or deep to it, and also various vessels including the external carotid artery, which is shown here, may be seen as well as the retro mandibular vein.

Submandibular Gland

The submandibular gland is located in the posterior submandibular triangle, and the borders include the anterior and posterior bellies of the digastric muscle and the bony mandible itself anteriorly, we see connective tissue and lymph nodes, and again, the lymph nodes around the submandibular gland are very common. Ultrasound is excellent for differentiating between nodes and other per salivary gland masses in this case, versus actually primary tumors that arise within the submandibular gland.

Posteriorly. The gland is bordered by the mylohyoid and high gloss muscles, and tubular structures are often seen within, normally this will be Wharton's duct. However, the facial artery may become more ectatic and somewhat, serpiginous and the two can be confused unless color doppler is placed on them, which makes the differentiation quite easy. Again, there is that normal homogeneously gray appearance to the submandibular gland itself.

The my myeloid, muscle as described, you can see on the left in this image. And, the artery is seen on the, right of this image, as shown by color. The duct of the gland may be seen posterior to it, as is shown in this image as well.

Sublingual Gland

And finally, the sub men sublingual gland. The sublingual gland is usually not something that we image, but may also be the location of tumors, but it's fairly unusual. The sublingual gland is located between the muscles of the floor of the oral cavity and laterally of course, the mandible itself. It's somewhat oval on transverse imaging and lenticular in longitudinal sections. And again, Wharton's duct coming out of the submandibular gland lies on its medial surface.

Again, you can see the shadowing, on the left hand side of this image. You can see the shadowing from the mandible, and you can see the various muscles in the floor of the mouth to the right of it in this image. And again, it has that relatively homogeneous gray scale appearance seen in all of the other, salivary glands.

Pathology Affecting the Salivary Glands

Now, the various things that affect the salivary glands include largely inflammatory processes and masses.

Acute Inflammatory Processes

Acute inflammatory processes are probably the most common form of pathology to affect the salivary glands. The patient typically presents with swollen, painful, often bilateral glands in children. We may see this with, viral infections such as mumps. In adults it tends to be more commonly bacterial, and staph aureus and various forms of oral flora may be responsible.

Graphically, we see enlarged relatively hypo coic glands that tend to be hypervascular by color and power doppler. Oftentimes there will be associated lymphadenopathy. And the main complication that we look for in these patients is the development of an inter glandular abscess says, again, typically acute s adenitis, will be seen as a hypervascular state. Oftentimes calculi may be identified within, and one may also find this, hypo coic nodular appearance that's seen. But this is very, very nonspecific and we'll talk about some of the other entities that can cause this in upcoming images.

Again, one of the complications that may occur in these patients is the development of an abscess. This is probably from a blocked infected duct, which then, develops kind of a life of its own and enlarges. These typically present as a hypoechoic uh, lesion, oftentimes with moving material within on gray scale evaluation and surrounding hyper vascularity on colored doppler.

Chronic Sialadenitis

Chronic style adenitis is also a relatively common phenomenon. These patients pre present with intermittently painful, swollen glands, either unilateral or bilateral. Oftentimes the pain is associated with food ingestion. On ultrasound, the glands may be normal to even small in size and tend to be hypoechoic and somewhat in homogeneous.

Again, that multiple small round lesion appearance that we saw on the previous slide, is probably more common in chronic s adenitis even than acute. Again, the differential for this is quite, extensive and acute includes both acute and chronic SIO adenitis as shown. But other granulomatous infections and sarcoid may cause it. Sjogren's is also a classic for producing this appearance and patients with HIV disease may have it as well. So a very non-specific appearance of these patients with multiple small round lesions.

Again, a classic appearance here in the upper part of the slide of chronic s adenitis, versus the opposite normal side. In the same patient, you can see the nice normal homogeneous appearance of the submandibular gland versus the hypoechoic in homogeneous appearance on the affected side, which as is very common, contains various, dilated ducts and again, often stones will develop another patient with diffuse duct ectasia, which presents as part of the overall, appearance of patients who have chronic s adenitis.

And again, in these patients, various ducts may be pinched off or blocked off, and again, these patients may develop abscesses as shown here with this hypoechoic or largely cystic mass with a fluid debris level. These can be punctured and drained percutaneously.

Here you can see a patient who has marked duct ectasia with a tender area, laterally, which after drainage was seen to just collapse. And at this point you can actually see the duct itself it with this rather beaded appearance that you see here.

Granulomatous Sialadenitis

Granuloma s adenitis is a non-specific finding. This is a patient who presented with a painful or mass, that came and went, in the area of the parotid gland. It was suspected of actually representing a mass. And on the CT scan, you can see there is an area which hyper enhances on the ultrasound. However, this was relatively homogeneous corson echogenicity without evidence of a mass dilatation of ducts, calculus, or any other abnormalities. And this actually came back after biopsy as granulomatous s adenitis. Again, a very, difficult diagnosis to make without biopsy.

Sialolithiasis

Ssis, of course, are stones within the gland, usually in dilated ducts. Typically this occurs in the submandibular gland said to occur in about 60 to 90% of patients. As was shown in the earlier patient that we looked at, the parotid gland is far less common accounting for about 10 to 20% of cases.

Again, it's a similar finding of obstruction with recurrent swelling and infection, formation of stones, which then again leads to more obstruction, recurrent swelling, and more infection. Radiographs, which have been said to be capable of finding these stones are relatively insensitive because many of the stones are radiolucent about 80%. The same would be for ct. Ultrasound is probably therefore the most sensitive technique. And also allows imaging of the surrounding dilated ductal system and any particularly dilated or debris filled areas which could represent abscesses.

Sjogren's Syndrome

Sjogren's syndrome is another inflammatory process that affects the salivary glands. This is actually a chronic lymphocytic or plasma cell infiltration. There is destruction of both the salivary and lacrimal glands, which can lead to patients presenting with a both dry eye and dry mouth phenomenon.

Typically this is a disease of women over 40 years of age and is often associated with lymphoproliferative disease. In general. Ultrasound is recommended for screening of possible lymphomas masses in these cases. And again, it is recommended in the literature that FNA may be indicated for lesions greater than two centimeters.

Again, the ultrasound findings are not specific. It may lead to glandular in homogeneity. And again, those multiple small hypo coic nodules, which we've shown in other cases are said to be relatively typical. This is such a case here. This was a 45-year-old woman. You can see that the salivary gland in this particular case is literally peppered, with these small hypo coic nodules.

Salivary Gland Neoplasms

Salivary gland neoplasms are relatively rare tumors. Luckily most of them are benign, about 70 to 80%, and the majority occur in the parotid gland. And the teaching tends to be that the smaller the salivary gland, the more likely lesions will be malignant. So in the parotid gland where 80 to 90% of these neoplasms will occur, only about a third or so will be malignant, in the submandibular gland, where only about 10 to 12% of lesions overall will occur, greater than 50% will be malignant. And again, the sublingual gland, although again, un uncommon, is something to be looked out for because they're, the incidence of malignancy is probably even higher.

Typically, these present as slow growing painless masses, although they may be tender in some cases. The list of benign lesions, which can occur in the salivary glands is relatively extensive. The most common two will be pleomorphic adenomas and war's tumor with a list of other both primary and mesenchymal lesions, such as heman or lipoma occurring as well. Cysts of course, and lymph nodes could be classified as benign lesions of the salivary gland as well. And are probably by far in a way the most common thing that we see. When we look at these areas.

Benign Neoplasms

Pleomorphic adenomas, typically occur in the parotid gland, female to male predo. There is a female to male predominance, and typically it occurs in the fourth to fifth decade of life. Usually they're solitary and unilateral, but they may undergo malignant transformation. Typically, these are treated with conservative, conservative surgery, such that the lobe or, or a part of the gland itself may be removed rather than radical surgery that would be performed for truly malignant lesions.

The ultrasound appearance is quite varied. Here's a classic pleomorphic adenoma of the parotid, where you see the homogeneous parotid, parenchyma around it. This multilobular in homogeneous relatively hypoechoic lesion, which can be contrasted with this cystic pleomorphic adenoma here, which has a, a great deal or a central area of, of fluid with various, areas of solid tissue. More peripherally.

Hans is of the other, most common of the benign tumors. This, has various, cell types involved and other names such as adeno lymphoma, have been applied to it. I think most people would stick with Han's tumors since it's easier to say. This actually comprises about five to 10% of overall salivary neoplasms, and the presentation tends to be a bit later in life than, pleomorphic adenomas occurring most typically in the fifth to sixth decade. And this has a male to female predominance rather than female to male as was seen with pleomorphic adenomas.

Typically, these are singular but may be multifocal. So again, important to scan both of, the or all of the, salivary glands in these examinations. And again, these may also undergo malignant transformation. The good thing about diagnosing war's tumor preoperatively is that it can be removed by a simple enucleation enucleation, sorry.

Again, the findings are relatively non-specific. Here's a patient showing a power doppler image of a warts tumor. You can see that this is well circumscribed quite in homogeneous with cystic and solid areas and moderately vascular by power doppler.

A parotid oncocytoma, relatively rare tumor. And again, very little that's specific about this. You can see this mass is relatively triangular on the surface of the gland and has areas of hypo and hyper echogenicity internally. Again, all of this, however, in my book, is relatively nonspecific as far as any of these tumor types go.

Heman is a lesion that's typically found in children and young adults and does have a somewhat suggestive ultrasound appearance. Typically they are kind of striated internally. Like other he angios, there may be internal bolli with posterior calcifications, and it's relatively vascular by color and power doppler. Interestingly enough, these are difficult to diagnose. Sonograph difficult to diagnose with FNA because oftentimes the aspirate will simply yield a large amount of blood.

This was a young man with a parotid hemangioma. You can see again that internally striated appearance, well circumscribed and by color and power doppler relatively vascular.

Again, cysts are probably the most common lesion identified within the salivary gland. Typically, these are not symptomatic, and are kinda leave alone lesions if you see them and you see a simple cystic structure within the parotid gland, assuming it's not tender or infected, in which case it could be an abscess. These are probably simple salivary gland cysts and can largely be ignored.

Epidermal inclusion cysts, on the other hand, tend to be filled with very thick viscous material, and more hypoechoic and maybe somewhat tender. This was a quite small lesion. We tried aspirating it in this case and got no material probably because it was so viscous. We then went to a larger needle for the aspiration, which is usually how we do it. If we do not get a aspirate using the 25 gauge needle, typically we'll go to a 22.

Perisalivary Masses

Now another use for ultrasound is in the differentiation between primary salivary masses and per salivary masses. Again, these are common and usually indistinguishable clinically by palpation. Ultrasound on the other hand, is highly accurate in this, in this job, the differential typically of per salivary gland masses, and most of these occur around the submandibular gland, is going to be adenopathy, both intra and extra glandular abscess formation and various cystic lesions such as brachial cleft or thyroglossal duct cyst.

Again, between the ultrasound appearance and an ultrasound guided FNA, we can arrive at a definitive diagnosis in most of these cases. Also do keep in mind that if nodes are present and there is any suspicion of lymphoma, the aspirate should undergo washings and scent to flow cytometry to be able to differentiate between benign reactive adenopathy and actual lymphoma.

This is a patient with a relatively nasty looking node. It was a submandibular node, does have an echogenic hilar region, and also has relatively orderly appearance of the vessels on color doppler, which I don't put a lot of faith in that. But nonetheless, this was biopsied and did turn out to be a simply reactive node. This was also a patient with a history of sarcoidosis. And again, if there is a question of adenopathy, it's always a good idea to send the specimen for flow cytometry to evaluate for possible lymphoma.

This is a patient who also presented with a relatively large submandibular mass. In this particular case, you can see that it's largely cystic, maybe a fu septi and some wall irregularity. Typically these will represent brachial cleft cysts, particularly if they're located laterally given the anatomy or the embryology of the development of these lesions.

Malignant Salivary Gland Lesions

Malignant salivary gland lesions, again, there's a relatively extensive differential group here. The most common would probably be muco epidermoid carcinoma and adenoid adenoid cystic carcinoma, as well as in the older population, squamous cell carcinoma.

Interestingly enough, muco epidermoid ca tends to be, aggressive In some cases, adenoid cystic carcinoma will present oftentimes with pain because it has a nasty habit of growing along the nerves and can actually invade the nerves along the base of a skull. And squamous cell carcinomas may be either metastatic from other head and neck lesions, or may actually be primary salivary lesions. Others are relatively uncommon, including a cynic cell. Primary adenocarcinoma, again, in older patients frequently think of metastasis from other head and neck primaries, and always keep in mind that lymphoma, either primary or systemic may affect the salivary glands as well.

Again, there's nothing specific about these either amongst themselves or when compared to the benign lesions. Here is what turned out to be a muco epidermoid carcinoma when biopsied, large heterogeneous lesion well-defined, with internal cystic spaces.

This is a patient with a squamous cell carcinoma. And these in our experience, are often very difficult to differentiate from an actual abscess. They have this fluctuate material internally that may be mobile oftentimes as is seen here, relatively hypervascular, for all the world. We suspected this was going to be an abscess and on aspiration turned out to be squamous cell carcinoma.

This is a large solid mass, which turned out to be a basiloid adenocarcinoma of the submandibular gland. Again, irregular branching vessels on color, but not terribly specific by imaging techniques. And this, again, very similar hypoechoic mass turns out to be a B-cell lymphoma.

I think if you look at the images that we've shown, you can see why I believe very strongly that fine needle biopsy of these lesions is important. And regardless of what some of the papers will say, basically in our book, they all tend to look alike. And I don't think you can differentiate benign from malignant, nor can you differentiate among the benign or malignant lesions on either side. And it's important to know what this is upfront because many of these lesions will not require surgery. Inflammatory process, infectious processes, lymphoma and mets will often be treated systemically or even with local chemo radiation, as opposed to actual surgery.

Also, an accurate preoperative diagnosis will allow for pre-op planning, in which case one may want to do either radical surgery, a nucleation, or a partial, parotidectomy. Among the salivary gland masses, again, the management is quite different. You have inflammatory processes, which will typically wind up with either steroids or antibiotic, versus lymphoid hyperplasia, which will simply be observed. And again, among the benign lesions, as we mentioned before, there may be o observation for things like lymphoma in nucleation for warts or partial resection for pleomorphic adenoma, and even among the malignant lesions, complete resection versus adjuvant chemotherapy, versus just chemotherapy or radiation for metastases and lymphoma. So an upfront diagnosis is a very important thing in our opinion.

Biopsy Techniques

There has been recent literature, recommending core needle biopsy, with ultrasound guidance. And the disadvantages of this is that it's a large needle in an ugly place right in your face. An incision is necessary, again, in your face. These can be large needles, and of course there is an issue potentially with seeding or bleeding.

We think that fine needle aspiration biopsy is an excellent technique in the evaluation of salivary and peri salivary lesions. Again, done under ultrasound guidance with no incision necessary. We've found no or minimal complication rate, and typically we use a 22 to 25 gauge needle. However, I think caution must be exercised here in that before you can expect to be able to differentiate these lesions with a fine needle aspiration, you must be certain that the cytology in your institution is excellent, otherwise you may need to revert back to core lesions because if they can't be diagnosed cytologically, they're going to need a larger specimen. And it is simply not possible in some areas of the world to have cytology. That is as good as we are lucky to have.

At USC, this is a pleomorphic adenoma, which is being biopsied within the parotid gland. And we actually did a study of the results of our patients. We had between a five in a five year period, we biopsied almost 50 of these patients, or 48 samples in 45 patients. We did a clinical outcome via chart review and surgical pathology, and published this in radiology in 2011.

Subsequent follow up, we found 45 patients who underwent, FNA, who were evaluable. We lost three, three were lost to follow up. 17 or 38% had operative invention intervention four, decline surgery 9% because of existing comorbidities that made surgery very difficult in them. And in fact, the, the benign FNA result, I think, allowed these patients to actually feel comfortable given the fact that they were poor surgical risks to simply follow up with ultrasound.

42% or 19 of our patients because of the biopsy results, had conservative management, and non-operative management. After di non-diagnostic FNA occurred in two or two patients or 4% of our population. Among the 17 per patients who underwent operative intervention, the procedures ranged from a simple ex al biopsy to total parotidectomy.

There was one non-diagnostic FNA that underwent surgery. This turned out to be a brachial cleft cyst and was largely based on the imaging and a negative cytology for cells. Surgical pathology corresponded to the FNA findings in 15 of 16 patients for 94%. In one case, the pathology did not correspond to the FNA findings, and unfortunately, this was a case of a giant cell tumor, which was actually located beneath a lymph node that was actually biopsied on top of it, which probably says that the person performing the examination or the FNA should be very, very careful to correlate the CT or MR findings if they're available. Before performing the ultrasound guided procedure,

20, 19 of our 45 patients were spared surgery. Seven of these had benign cysts. Seven of them had inflammatory processes. Three were diagnosed with metastatic disease, one with lymphoma, and one had a non-diagnostic result that was followed. And again, the management of these tends to be, various steroids, chemotherapy, radiation, intervention or even, non-surgical intervention or simple observation.

Among the few patients, the 8% or four patients that had a non diagno three patients had a non-diagnostic FNA. There were four procedures with three patients. Two of these still had non-operative management. One patient was followed for nine months, after, aspiration and a marked decrease in size of the, lesion after FNA with aspiration of fluid. The second patient was followed for 24 months. And this was a small lesion that showed no change. One patient did undergo operative management, and that was the patient who underwent superficial parotidectomy, for a brachial cleft cyst.

Conclusion

So, in conclusion, in our opinion, most actual mass like lesions in the salivary gland tend to look alike. Salivary gland aspiration, fine needle aspiration is safe, easy and well tolerated. But again, really excellent cytology is necessary to be able to make these calls upfront. Otherwise, it may be necessary to resort to the core biopsies with larger needles.

You may want to get culture and sensitivity on the material depending on the symptoms, and if it looks like it could be a nodal mass, always be certain that the material is washed for flow cytometry. Again, I think using FNA in these patients spares a, a large number of patients from possible surgery or more interventional techniques, it allows the surgeon to direct treatment and surgical planning.

Thank you.