British Journal of Radiology (2005) 78, 362-369
© 2005 British Institute of Radiology
doi: 10.1259/bjr/93120352
Diseases of the submandibular gland as demonstrated using high resolution ultrasound
F Alyas, MRCP1,
K Lewis2,
M Williams, FDS, FRCS2,
A B Moody, FDS, FRCS2,
K T Wong, FRCR3,
A T Ahuja, FRCR3 and
D C Howlett, MRCP, FRCR1
1 Department of Radiology, 2 Department of Maxillofacial Surgery, Eastbourne District General Hospital, Eastbourne, UK and 3 Department of Diagnostic Radiology and Organ Imaging, Prince of Wales Hospital, Hong Kong
Correspondence: Dr David Howlett, Consultant Radiologist, Department of Radiology, Kings Drive, Eastbourne, East Sussex BN21 2UD, UK
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Abstract
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In this review the high resolution ultrasound appearances of the normal anatomy and pathology involving the submandibular gland are demonstrated. The submandibular gland is affected by a number of disease processes that may be difficult to distinguish clinically. Its superficial location makes it ideal for ultrasound evaluation and a useful adjunct to clinical examination. In the assessment of submandibular pathology ultrasound allows intraglandular and extraglandular lesions to be localized and differentiated. These lesions can be further characterized as being benign or malignant and the extent of any extraglandular extension determined. Ultrasound is the first-line investigation in the assessment of sialolithiasis due to its high specificity and sensitivity. In severe infective sialadenitis ultrasound can confirm the presence and guide drainage of abscesses. Ultrasound also has an important role in the assessment of chronic inflammatory disorders such as sarcoidosis and Sjögren's syndrome.
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Introduction
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High resolution ultrasound is a safe, inexpensive and accurate method of assessing the extent and nature of submandibular disease, providing valuable information to guide further imaging and management. The ultrasound appearances of the normal glandular anatomy, together with common and more unusual pathologies that may involve the submandibular gland will be considered in this review.
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Normal ultrasound anatomy and relations of the submandibular gland
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The submandibular gland lies within the submandibular triangle in the plane of the anterior belly of the digastric muscle. The submandibular gland has a homogeneous echotexture on ultrasound which is slightly hyperechoic compared with surrounding muscle. Intraglandular ducts may be identified as small linear hyperechoic stripes (Figure 1
). There is a larger superficial lobe and a smaller and more posterior deep lobe which connect around the posterior border of the mylohyoid muscle. In ultrasound evaluation of the gland isolation of pathology to a particular lobe is not relevant clinically as the surgical treatments are the same [1, 2].
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Figure 1. Axial ultrasound through a normal right submandibular gland showing its relationship to adjacent structures. S, submandibular gland; M, mylohyoid muscle; H, hyoglossus muscle; White arrow, intraglandular duct; D, posterior belly of digastric muscle.
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Wharton's duct appears as tubular structure which may be apparent on ultrasound. It is best seen when pathologically dilated but may be demonstrable in normal subjects. The duct emerges from the hilum of the submandibular gland and passes medially around the posterior border of mylohyoid (Figure 2). It then courses medial to the sublingual gland to the papilla in the floor of the mouth. The path of Wharton's duct is best viewed in a slightly oblique plane [1, 2].
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Figure 2. Oblique axial ultrasound through a normal left submandibular gland demonstrating the normal Wharton's duct. Small white arrow, Wharton's duct; Large white arrow, mylohyoid muscle.
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Relations to the gland are as follows. Anteriorly to the gland is a fat filled triangular space. Superomedially and deep to mylohyoid, is the lingual vein. Posteriorly lies the retromandibular vein, laterally the facial vein and inferiorly platysma and subcutaneous tissue. There are several regional lymph node groups surrounding the gland although normal lymph nodes are not found within gland, unlike the parotids, due to early glandular encapsulation. During ultrasound examination it is important to be aware of the Küttner lymph node. Its close relationship to the posterior of the submandibular gland (also just adjacent to the parotid gland) means it should not be mistaken for submandibular pathology (Figure 3).
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Figure 3. Oblique axial ultrasound through a normal right submandibular gland demonstrating the position of the Küttner lymph node. P, parotid gland; White arrow, Küttner lymph node; R, retromandibular vein; S, submandibular gland.
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Pathological processes involving the submandibular gland
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Sialolithiasis
Salivary gland calculi most commonly occur in the submandibular glands and this reflects the more mucinous content of submandibular secretions. 90% of calculi are radio opaque [1] and they are multiple in 25% of patients [2]. Ultrasound has a high degree of accuracy (96%) in their diagnosis [3].
Most calculi (85%), occur in Wharton's duct while the remainder (15%) are found within the gland (Figure 4) or at the ductal hilum. Most commonly calculi impact at the curvature of Wharton's duct as it goes around mylohyoid (35%) [2]. Ductal stones may cause an obstruction or stricture causing dilatation of the main duct and proximal intraglandular ducts which will be visible on ultrasound. One third of Wharton's duct calculi occur at the ostium and small stones here are difficult to visualize, however consequent main duct dilation is visible in 65% of these cases [4] (Figure 5).
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Figure 4. Ultrasound of left submandibular gland demonstrating intraglandular sialolithiasis. Note the two large hyperechoic calculi within the gland that cast acoustic shadows.
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Figure 5. Ultrasound demonstrating sialolithiasis with dilatation of Wharton's duct (small white arrows) secondary to a meatal stone (not shown, see text). There is a non-obstructing intraductal calculus within Wharton's duct casting an acoustic shadow (large white arrow), together with sludge. S, submandibular gland.
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On ultrasound stones appear as hyperechoic foci casting posterior acoustic shadowing (Figure 4
). Those smaller than 2 mm may not cast acoustic shadows.
Ultrasound can also assess the complications of calculi, e.g. sialadenitis, sialocele, abscess and in chronic circumstances gland atrophy (see later).
Sialadenitis
This can be sub-divided into acute and chronic sialadenitis.
Acute sialadenitis
The majority of infections have a viral aetiology (most commonly mumps) and do not require imaging routinely. Bacterial infections are usually a result of salivary stasis allowing retrograde passage of organisms. This is common in the elderly/debilitated, following surgery, dehydration, trauma, irradiation, and in relation to obstructing lesions such as stones, tumours and strictures [2]. The most common causative organisms are Staphylococcus aureus or Streptococcus viridans.
In acute sialadenitis the gland appears enlarged and hypoechoic on ultrasound [5]. Ultrasound is useful in severe cases of bacterial infection, especially if abscess formation is suspected. Abscesses are seen as ill-defined hypoechoic foci, with intraglandular ducts passing through the lesion as opposed to ductal displacement, which would favour tumour. There may be adjacent regional lympadenopathy [2] (Figure 6). Ultrasound can also be used to guide drainage of suspected abscess.
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Figure 6. Ultrasound demonstrating a submandibular abscess in a man who presented with an acutely painful and enlarged gland. There is an ill-defined intraglandular hypoechoic mass and adjacent enlarged reactive lymph node (white arrow). Under ultrasound guidance pus was aspirated and subsequent culture grew Staphylococcus aureus. S, submandibular gland.
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Primary tuberculosis rarely presents in the submandibular gland and involvement usually occurs as a result of haematogenous dissemination or spread from adjacent structures and lymph nodes [2]. It can present acutely with sialadenitis or subacutely mimicking tumour [2]. Overall the imaging features are non-specific although a mixed echogenicity mass lesion may be seen (Figure 7).
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Figure 7. Ultrasound demonstrating intraglandular tuberculous abscess. There is a complex mass (callipers) in the submandibular gland with a central necrotic abscess cavity. Excision confirmed involvement of the gland with Mycobacterium tuberculosis.
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Chronic sialadenitis
Infective causes
Chronic sialadenitis is mainly caused by infection secondary to sialolithiasis. With recurrent infection the gland atrophies and is replaced by fibrotic tissue (Figure 8). Sonographically the gland appears atrophic and diffusely hypoechoic with irregular margins, the ultrasound appearances often simulating a "cirrhotic" liver [6]. There is an association between chronic infection, e.g. secondary to dental sepsis and duct stricture formation also.
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Figure 8. Ultrasound of left submandibular gland demonstrating chronic sialadenitis secondary to stone disease. S, atrophic, hypoechoic, irregular gland. Note the associated intraglandular calculus (callipers).
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Küttner tumour (chronic sclerosing sialadenitis) is a focal lesion resulting from chronic inflammation of the submandibular gland usually caused by bacterial infection or duct obstruction and these lesions may have a pseudotumour appearance. Biopsy or excision is often needed to confirm the diagnosis. Sonographically these lesions can mimic tumours appearing as a focal, hypoechoic lesion (Figure 9). Colour flow Doppler examination shows with a radial branching vascular pattern within the mass [6] (Figure 10).
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Figure 9. Ultrasound of the right submandibular gland demonstrating a Küttner tumour. There is a well-defined, hypoechoic mass in the submandibular gland, which could be mistaken, clinically and sonographically for a tumour. Diagnosis of chronic inflammation was confirmed by core biopsy and subsequent excision.
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Figure 10. Ultrasound of the same patient as in Figure 9 demonstrating increased radial flow on Doppler examination within the lesion.
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Non-infective causes
Sarcoidosis is a non-caseating granulomatous condition more usually affecting the parotids, with parotid involvement described in 6% of patients [1]. It may also affect the submandibular glands [2], presenting clinically with painless enlargement [1].
The ultrasound features of sarcoidosis in the submandibular gland are not well described although we have observed appearances similar to those described in the parotid gland. The appearances of sarcoidosis in the parotid are non-specific [1]. A variety of manifestations may be seen ranging from multiple hypoechoic foci to diffuse hypoechoic glandular enlargement (Figure 11) and there may be associated lymphadenopathy [1, 5]. The gland may be hypervascular on colour Doppler flow studies. Necrosis is not a feature in sarcoidosis and this may help in distinguishing it from tuberculosis [7].
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Figure 11. Ultrasound of the left submandibular gland in a patient with suspected thoracic sarcoidosis and painless salivary gland enlargement. The submandibular gland is enlarged, heterogeneous in texture and hypoechoic. Subsequent glandular biopsy confirmed the presence of sarcoid granulomata.
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Sjögren's syndrome is an autoimmune syndrome which consists of dry mucus membranes (e.g. eyes and mouth) and a connective tissue disorder predominantly affecting middle-aged women. Parotid or submandibular enlargement occurs in 80% of patients [2]. An appreciation of the underlying pathology is helpful in understanding the variety of ultrasound appearances. Initially there is inflammation involving the peripheral ductal system which results in intraglandular duct dilation and destruction of gland tissue predisposing to recurrent infection.
The progression of ultrasound changes reflects the various stages of this inflammatory process. Initially ultrasound of the gland may be normal, then showing diffuse gland enlargement, inhomogeneity and then sialectasis (shown in Figure 12) [8]. On colour Doppler flow assessment there is hypervascularity [9]. It is worth mentioning that the lacrimal glands are also frequently involved and are easily examined at the same time. They may often show similar ultrasound appearances to the submandibular gland (Figure 13).
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Figure 12. Submandibular ultrasound in a patient with Sjögren's syndrome. The gland is diffusely enlarged and of heterogeneous echotexture. Note the hypoechoic foci within the gland representing early sialectatic changes.
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Figure 13. Ultrasound of the lacrimal gland in a patient with Sjögren's syndrome. There are hypoechoic foci present within the enlarged gland (white arrow), which has a similar appearance to the submandibular gland in Figure 12.
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As the disease progresses numerous cystic spaces are seen reflecting progressive glandular destruction and prominent intraglandular sialectasis [8, 9] (Figure 14). These appearances are similar to those recognized in the parotid in HIV infection [10]. In end stage disease the gland becomes fibrotic and atrophic [11]. As these patients are at increased risk of lymphoma development ultrasound has been advocated as a surveillance tool by some authors [11].
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Figure 14. Ultrasound of the left submandibular gland demonstrating numerous prominent cystic spaces typical of florid sialectasis in Sjögren's syndrome. A similar appearance can occur in HIV infection.
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Tumours
The overall incidence of salivary gland tumours in the general population is 3%. They are more frequent in the parotid gland with only 14% of salivary gland tumours occurring in the submandibular gland. However there is a greater of incidence of malignancy in submandibular gland tumours (approximately half of all submandibular gland tumours are malignant [2] compared with 10% of all parotid tumours [1]) and the sonographer should be vigilant when ultrasound examination is performed in this respect. If a suspected neoplasm is identified within the gland ultrasound can then be used to guide fine needle aspiration (FNA) or core biopsy of the lesion to confirm its nature. FNA is a quick, safe and accurate technique, although core biopsy does provide an alternative with potential advantages [12].
Ultrasound will act as a guide to the need for further imaging, either CT or MRI, for sonographically malignant lesions or large lesions whose extent is difficult to access on ultrasound alone.
Benign tumours
Pleomorphic adenoma is the most common neoplasm of the submandibluar gland accounting for the majority of benign tumours [2]. On ultrasound these tumours appear as circumscribed, round, hypoechoic masses with a lobulated border, which may show posterior acoustic enhancement [2] (Figure 15). 25% of pleomorphic adenomas are associated with smaller satellite lesions [1]. Larger tumours may appear more atypical, developing areas of internal necrosis or haemorrhage and cystic changes or areas of calcification may occur [13]. Malignant transformation to adenocarcinoma is rare but should be suspected in patients with long standing tumours that become painful or grow rapidly.
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Figure 15. Ultrasound demonstrating submandibular gland pleomorphic adenoma. This lesion appears rounded, well defined and hypoechoic with distal acoustic enhancement present.
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Warthin's tumour (Cystadenolymphoma) although relatively common in the parotid is very unusual in the submandibular gland. Early encapsulation of the submandibular gland during fetal development prevents structures from the lymphatic, vascular and nervous system developing within the gland. This in turn makes disease of the lymphatic tissue, such as Warthin's tumour (and lymphoma), rare in the submandibular gland [2]. This is in contrast to the parotid gland which undergoes delayed encapsulation where such pathologies are relatively more common.
Oncocytoma is a rarely described tumour accounting for 1% of all salivary gland tumours, 11% of which occur in the submandibular gland. Histologically oncocytoma is composed of oncocytes derived from striated duct cells. It may relate to previous irradiation and can undergo malignant transformation. It appears similar to pleomorphic adenoma on ultrasound [1] (Figure 16).
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Figure 16. Submandibular ultrasound demonstrating an oncocytoma confirmed on gland excision. It has a similar appearance to pleomorphic adenoma (see Figure 15).
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Malignant tumours
There are several histological subtypes of primary malignant submandibular tumours, the most common being adenoid cystic carcinoma, followed by mucoepidermoid carcinoma and other sub-types such as acinic cell carcinoma and adenocarcinoma are rare [1]. Adenoid cystic carcinoma occurs in patients in their fifth or sixth decade [2], accounting for 17% of all submandibular tumours [1]. It can be multiple, has a propensity for perivascular and perineural spread and can metastasise to regional lymph nodes, lung and bone [2]. Ultrasound is able to distinguish benign from malignant tumours in 80% of cases [1]. It is also able to demonstrate extracapsular spread and any regional lymph node involvement. However it cannot distinguish between the different subtypes of malignant tumours. These appear similarly as masses of heterogeneous echotexture (Figure 17) with irregular infiltrating borders (Figure 18), and associated posterior acoustic shadowing. On colour Doppler examination malignant tumours may show multiple, irregular internal vessels, with hypervascularity and high resistance arterial flow [14]. Studies mainly performed on the parotid gland have shown that a resistive index (RI)<0.8 and pulsatility index (PI)<1.8 favours a benign over a malignant lesion [15]. It should be noted that small, low grade malignant tumours may appear benign on ultrasound and that histological confirmation should always be obtained.
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Figure 17. Submandibular ultrasound in a patient with an intraglandular adenoid cystic carcinoma. This appears as an ill-defined, hypoechoic and inhomogeneous mass.
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Figure 18. Submandibular ultrasound in a patient with mucoepidermoid carcinoma (large white arrow). Sonographically the features shown are similar to the adenoid cystic carcinoma in Figure 17. Note that in this case there is also extraglandular extension of tumour with invasion of the subcutaneous tissues and skin (small white arrows).
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Lymphoma
Primary lymphoma rarely occurs in the submandibular gland for reasons that have already been described and the gland is usually involved secondarily via haematogenous spread [7]. Primary disease may occur in patients with Sjögren's syndrome who are at significantly increased risk of developing a non-Hodgkin's lymphoma in particular [2].
The ultrasound features of lymphoma within the submandibular gland are rarely described [16] and lesions may appear as solid, hypoechoic or pseudocystic masses (Figure 19).
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Figure 19. Ultrasound demonstrating lymphoma of the submandibular gland confirmed with biopsy. There is a large, hypoechoic intraglandular mass. This patient had known disseminated B-cell lymphoma.
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Metastasis
Metastases to the submandibular gland are rare, occurring mainly as a result of haematogenous spread. These are mainly from head and neck tumours or melanoma. The ultrasound features of submandibular gland metastases are not well described, although the appearances are likely to be similar to these demonstrated in parotid metastatic disease [13]. Parotid metastases can vary in appearance but tend to be hypoechoic, with heterogeneous internal architecture and poorly defined margins [13].
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Conclusion
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High-resolution ultrasound is the initial imaging tool of choice for the evaluation of the symptomatic submandibular gland and adjacent structures. As well as providing information on the site, nature and extent of submandibular pathology, ultrasound can be used in the guidance of FNA, core biopsy and abscess drainage. Ultrasound is also able to act as a guide to the need for further imaging, usually with CT or MRI.
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Acknowledgments
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The authors would like Nick Taylor for preparation of the illustrations.
Received for publication February 27, 2004.
Revision received September 20, 2004.
Accepted for publication October 26, 2004.
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References
|
|---|
- Bradley MJ. Chapter 2: Salivary glands. In: Ahuja A, Evans R, editors. Practical head and neck ultrasound. London: Greenwich Medical Media, 2000; 19–37.
- Silvers AR, Som PM. Salivary glands. Radiol Clin N Am 1998;36:941–66.[CrossRef][Medline]
- Gritzmann N. Sonography of the salivary glands. AJR Am J Roentgenol 1989;53:161–6.
- Ching ASC, Ahuja AT. High resolution sonography of the submandibular space: anatomy and abnormalities. AJR Am J Roentgenol 2002;179:703–8.[Free Full Text]
- Koischwitz D, Gritmann N. Ultrasound of the neck. Radiol Clin N Am 2000;38:1029–43.[CrossRef][Medline]
- Ahuja AT, Richards PS, Wong KT, King AD, Yuen HY, Ching AS. Küttner tumour (chronic sclerosing sialadenitis) of the submandibular gland: sonographic appearances. Ultrasound Med Biol 2003;29:913–9.[CrossRef][Medline]
- Fischer T, Filimonow S, Petersein J, Zimmer C, Beyersdorff D, Guski H. Diagnosis of Heerfordt's syndrome by state-of-the-art ultrasound in combination with parotid biopsy: a case report. Eur Radiol 2002;12:134–7.[CrossRef][Medline]
- Makula E, Pokorny G, Rajtar M, Kiss I, Kovacs A, Kovacs L. Parotid gland ultrasonography as a diagnostic tool in primary Sjögren's syndrome. Br J Rheumatol 1996;35:972–7.[Abstract/Free Full Text]
- Martinoli C, Derchi LE, Solbiati L, Rizzatto G, Silvestri E, Giannoni M. Colour Doppler sonography of salivary glands. AJR Am J Roentgenol 1994;163:933–41.[Abstract/Free Full Text]
- Gooding GA, Sooy CD, Hybarger CP. Ultrasonography of cystic parotid lesions in HIV infection. Similarity of sonographic appearance with Sjögren's syndrome. J Ultrasound Med 1992;11:35–9.[Abstract]
- Ahuja AT, Metreweli C. Ultrasound features of Sjögren's syndrome. Australas Radiol 1996;40:10–4.[Medline]
- Kesse KW, Manjaly G, Violaris N, Howlett DC. Ultrasound guided biopsy in the evaluation of focal lesions and diffuse swelling of the parotid gland. Br J Oral Maxillofac Surg 2002;40:384–8.[CrossRef][Medline]
- Howlett DC. High-resolution ultrasound assessment of the parotid gland. Br J Radiol 2003;76:271–7.[Abstract/Free Full Text]
- Martinoli C, Derchi LE, Solbiati L, Rizzatto G, Silvestri E, Giannoni M. Colour Doppler sonography of salivary glands. AJR Am J Roentgenol 1994;163:933–41.
- Bradley MJ, Durham LH, Lancer JM. The role of colour flow Doppler in the investigation of the salivary gland tumour. Clin Radiol 2000;55:759–62.[CrossRef][Medline]
- Yasumoto M, Yoshimura R, Sunaba K, Shibuya H. Sonographic appearances of malignant lymphoma of the salivary glands. J Clin Ultrasound 2001;29:491–8.[CrossRef][Medline]
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Abstract
Introduction
