Imaging of Salivary Glands Tumours

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European Journal of Radiology 66 (2008) 419–436

Imaging of salivary gland tumours

Y.Y.P. Lee, K.T. Wong, A.D. King, A.T. Ahuja ∗Department of Diagnostic Radiology & Organ Imaging, The Chinese University of Hong Kong,

Prince of Wales Hospital, Shatin NT, Hong Kong SAR

Received 11 January 2008; received in revised form 11 January 2008; accepted 14 January 2008

bstract

Salivary gland neoplasms account for <3% of all tumors. Most of them are benign and parotid gland is the commonest site. As a general rule,he smaller the involved salivary gland, the higher is the possibility of the tumor being malignant. The role of imaging in assessment of salivaryland tumour is to define intra-glandular vs. extra-glandular location, detect malignant features, assess local extension and invasion, detect nodaletastases and systemic involvement. Image guided fine needle aspiration cytology provides a safe means to obtain cytological confirmation.For lesions in the superficial parotid and submandibular gland, ultrasound is an ideal tool for initial assessment. These are superficial structures

ccessible by high resolution ultrasound and FNAC which provides excellent resolution and tissue characterization without a radiation hazard.odal involvement can also be assessed. If deep tissue extension is suspected or malignancy confirmed on cytology, an MRI or CT is mandatory

o evaluate tumour extent, local invasion and perineural spread. For all tumours in the sublingual gland, MRI should be performed as the risk ofalignancy is high.For lesions of the deep lobe of parotid gland and the minor salivary glands, MRI and CT are the modalities of choice. Ultrasound has limited

isualization of the deep lobe of parotid gland which is obscured by the mandible. Minor salivary gland lesions in the mucosa of oral cavity,
harynx and tracheo-bronchial tree, are also not accessible by conventional ultrasound.
Recent study suggests that MR spectroscopy may differentiate malignant and benign salivary gland tumours as well as distinguishing Warthin’sumor from pleomorphic adenoma. However, its role in clinical practice is not well established. Similarly, the role of nuclear medicine and PET scan,n imaging of parotid masses is limited. Sialography is used to delineate the salivary ductal system and has limited role in assessment of tumour extent.

2008 Elsevier Ireland Ltd. All rights reserved.

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eywords: Salivary gland tumours; Imaging; Ultrasound; CT; MR

. Introduction

Salivary gland neoplasms account for <3% of all tumours1]. Most of them are benign and parotid gland is the common-st site. As a general rule, the smaller the involved salivary gland,he higher is the possibility of the tumour being malignant. Theercentage of malignant salivary gland tumours are: 20–30% inarotid gland, 45–60% in submandibular gland, 70–85% in sub-ingual gland and 49–80% in other minor salivary gland [2–4].maging of salivary gland tumour serves to define malignanteatures, differentiate it from benign mimics, assess local inva-
ion and regional spread. Image guided fine needle aspirationytology provides a safe means to obtain cytological confirma-ion and to differentiate benign salivary gland tumour from itsow-grade malignant counterpart.
∗ Corresponding author. Fax: +852 2648 7269.E-mail address: [email protected] (A.T. Ahuja).

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720-048X/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved.oi:10.1016/j.ejrad.2008.01.027

. Clinical presentation

Adenoid cystic carcinoma is seen in adults with slight femaleredominance while mucoepidermoid carcinoma has no age orex predeliction. The other malignant salivary gland tumours areeen in adults with slight male-predominance [5,6].

Most patients presented with a painless, progressive enlarg-ng mass in the region of salivary gland or in mucosal spacef oral cavity in the case of minor salivary gland tumour. Theasses are firm to hard on palpation, mobile if within the sali-

ary gland and fixed when there is local invasion. The higherhe histological grade, the faster the tumour enlargement. Minoralivary gland malignancies may present as mucosal ulceration.

Pain is experienced in 5.1% of patients with benign sali-ary gland tumours and 6.5% of patients with its malignant
ounterpart [7]. Therefore, pain is not a good indicator ofenignity or malignancy. However, in patients with provenalivary gland carcinoma, the prognosis is worse in those pre-enting with constant pain. The 5-year-survival drops from
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8% to 35% in patients without and with pain at presentation8].

Neurological symptoms involving cranial nerves are seen inatients with perineural spread, local neural invasion or irri-ation. The commonest symptoms are those involving facialerve (CN VII) as most of the carcinomas occur in the parotidland. The symptoms include facial pain, facial itchiness, otal-ia and facial nerve paralysis. Facial nerve paralysis correlatesith poor prognosis and increased incidence of nodal metastases

66–77%) with a 5-year-survival rate of 9–14%. [8]The third branch (CN V3) of the trigeminal nerve may be

nvolved if the tumour is in the deep lobe of parotid gland. Thelossopharyngeal nerve (CN IX), vagus nerve (CN X), accessoryerve (XI) and hypoglossal nerve (CN XII) may be involved by
umour extension to the deep tissue of upper neck or by perineu-al spread. Hoarseness of voice, aspiration, shoulder dysfunctionnd atrophy of hemitongue are the related symptoms.
ig. 1. Gadolinium enhanced T1W axial (a) and fat suppressed coronal scanb) show the internal necrosis, thick, ill-defined enhancing walls of a malignantarotid lesion (arrows) although ultrasound, CT, MR can identify malignantesions, they are unable to distinguish between the types of malignancies.

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f Radiology 66 (2008) 419–436

Lymph node metastases may be clinically detected as a firmeck lump. The parotid and submandibular glands first drain tohe deep cervical chain while sublingual gland drains to sub-

ental and submandibular nodes. Retropharyngeal nodes arehe first station of nodal drainage from oropharyngeal mucosa.he presence of metastatic node in patients with malignant sali-ary gland tumour is associated with poorer prognosis. The0-year-survival of those without nodal metastasis is 63% whilehose with nodal metastasis are 33%. In patients with parotidland carcinoma, nodal metastasis is most commonly seen inucoepidermoid carcinoma, followed by squamous cell car-

inoma. In patients with submandibular, sublingual and minoralivary gland cancer, nodal spread is most commonly seen inarcinoma-ex-pleomorphic adenoma.

Distant metastasis is an indicator of poor prognosis. It is seenn 20% of the parotid cancers, most commonly from adenoidystic carcinoma, followed by undifferentiated carcinoma [8].

. The use and choice of imaging

The role of imaging in assessment of salivary gland tumours to define intra-glandular vs. extra-glandular location, detect

alignant features, assess local extension and invasion andetect nodal metastases and systemic involvement.

For lesions in the parotid, submandibular and sublinguallands, ultrasound is an ideal tool for initial assessment.
hese are relatively superficial structures accessible by high-
esolution ultrasound, which provides excellent resolution andissue characterization without a radiation hazard. Cervical nodenvolvement can also be assessed. It is readily combined with

ig. 2. Grey-scale ultrasound shows an infiltrative, ill-defined, solid, hypoe-hoic mass (arrows) overlying the ramus of the mandibular (arrowheads). Theppearances are typical of a malignant parotid mass.

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At our center, if a patient presents with signs and symp-toms suggestive of a malignant tumour, or tumour of minorsalivary glands, MR is the initial investigation of choice. Ultra-

Y.Y.P. Lee et al. / European Jour

ne needle aspiration cytology (FNAC) and if there is a deep tis-ue extension suspected or malignancy confirmed on cytology,n MRI or CT is mandatory to evaluate the complete tumourxtent, local invasion and perineural spread. For all tumoursetected in the sublingual gland, an MRI should be performeds the risk of malignancy is high.

For lesions of the deep lobe of parotid gland and the minoralivary glands, MRI and CT are the modalities of choice. Ultra-ound has limited visualization of the deep lobe of parotid gland,hich is also partially obscured by the body of the mandible.inor salivary gland lesions are seen in the mucosa of oral cav-

ty, pharynx and tracheo-bronchial tree, which are not accessibley conventional ultrasound. Moreover, the first station nodalrainage from oral cavity and pharyngeal mucosal space isetropharyngeal nodes, which is also not accessible by conven-ional ultrasound.

High-resolution ultrasound provides excellent tissue charac-erization, multi-planar information and vascular pattern withoppler technique. It is also an optimal tool to guide fine nee-le aspiration cytology with its ready availability and ability torovide real time image guidance. The use of ultrasound is, how-ver, limited to superficial structures and the accuracy dependantn specialist expertise. Minor salivary gland lesions, deep tissuenvolvement, perineural spread, bony invasion and oropharyn-eal/retropharyngeal nodes are not accessed by conventionalltrasound technique [7].

MRI and CT are optimal to delineate complete tumour extentnd regional lymphadenopathy. MRI is superior in its soft tissueifferentiation. It is particularly helpful in detecting deep tis-ue extension, marrow infiltration/edema, perineural spread andhe parotid portion of facial nerve using high-resolution tech-
iques. It also detects signal change and extra-capsular spreadn regional lymph nodes and does not involve the use of ionizingadiation.
ig. 3. Corresponding CECT demonstrates enhancement within the massarrow), its location and extent and infiltration into the overlying subcutaneousissue, which is thickened. Ultrasound readily identifies a malignant mass in theuperficial lobe and helps to guide a biopsy. However, CT/MR are much better indentifying the exact location of the lesion, its adjacent and distant involvement,articularly perineural extension.

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Radiology 66 (2008) 419–436 421

The disadvantage of MRI is the relative high cost, suscep-ibility to motion artifacts and poorer cortical bone delineationompared to CT. When bony erosion is a concern, such as inalatal minor salivary gland malignancy, CT may be required.

The role of nuclear medicine and PET scan, in imagingf parotid masses has not yet been established [9]. Warthin’sumour and oncocytoma are the only salivary gland tumourshat accumulate Tc99m Pertechnetate. Sialography is used toelineate the salivary ductal system and has a limited role inssessment of tumour extent.

ig. 4. Axial grey-scale ultrasound (a) shows an ill-defined, hypoechoic, het-rogeneous mass (arrows) in the superficial lobe of the parotid gland. Notehe internal areas of necrosis and prominent vessels on Doppler ultrasound (b).lthough it demonstrates posterior enhancement similar to pleomorphic ade-oma, the presence of ill-defined edges and internal necrosis makes the lesionsuspicious. A biopsy confirmed its malignant nature.

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in counseling the patient about the risk of facial nerve dam-age, the need for neck dissection is immense. Hence, it is oftenroutinely used in the assessment of salivary gland tumour.


ound may be used following a MR for an image-guided biopsy.or tumour of submandibular gland, superficial lobe of parotidwhere majority of tumours are benign), ultrasound (combinedith FNAC) often provides the necessary information for treat-ent planning.In institution with access to MR, the role of CT in evalu-

ting salivary gland tumour is limited. CT evaluates corticalnvolvement better and presence of calculus disease in sialadeni-is (which may mimic a tumour); but MR is superior in definingumour characteristics, extension particularly perineural spread.n evaluating salivary gland tumour, both MR and CT assessimilar features such as internal homogenicity/heterogenicity,ll-defined edge, extra glandular extension, enhancement patternnd presence of adjacent malignant nodes.

. The role of fine needle aspiration cytology (FNAC)

Fine needle aspiration cytology (FNAC) is routinelyecommended as some of the tumours have overlapping appear-nces. A definitive histological diagnosis and grading of

ig. 5. Grey-scale ultrasound (a) of the submandibular gland showing and ill-efined, hypoechoic, heterogeneous mass (arrows) with cystic areas and intra-odular scattered vascularity on Doppler (b).

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f Radiology 66 (2008) 419–436

alignancy helps to guide treatment and facilitate patientounseling.

However, FNAC is again dependant on availability of exper-ise and the reported sensitivity and specificity for FNAC is8–93% and 75–99%, respectively [10–12].

It has also been reported that cytology and imaging areomparable in their ability to identify malignant lesions pre-peratively. The sensitivity and specificity of MRI has beeneported 88% and 77%, respectively, and for CT, the sen-itivity and specificity reported is 100% and 42% [13],espectively.

When a definitive diagnosis is established on FNAC, its help

ig. 6. Grey-scale (a) ultrasound of the submandibular gland shows a well-efined, isoechoic, heterogeneous mass (arrows) with marked intranodularascularity on Doppler (b). Biopsy revealed a malignant salivary tumour. Irre-pective of imaging appearances, the index of suspicion for malignancy is highor submandibular tumours.

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twsttateinaceous fluid within benign tumours may give rise tointermediate T1 signal, mimicking malignancy. Benign pathol-ogy tends to have relatively homongeous signal intensity.Intra-tumoural hemorrhage and calcification may result in


. Imaging features of malignant salivary glandumours

Malignant carcinomas shares similar imaging features, andenerally cannot be differentiated from one another by imag-ng alone (Fig. 1). The role of imaging is mainly to detect

alignant features, demonstrate local and distant involvement,efine nodal status and guide FNAC. The subsequent para-raphs discuss the general features of salivary gland malignancynd specific features, if any, are discussed under individualumours.

.1. MR and CT feature

T1W sequence typically shows the tumours well against theackground of fatty content in parotid gland. T2W fat suppressedequence defines fluid contents while post-gadolinium T1W fatuppressed sequence demonstrate tumour enhancement pattern.

.1.1. High-grade carcinomaAn aggressive salivary gland tumour typically shows ill-

efined, infiltrative border, heterogeneous internal signal withystic change and necrosis assessed both by MR and CTFigs. 2 and 3). The internal signal is characteristically low-o-intermediate on both T1W and T2W images. After contrastboth MR and CT) enhancement, the lesions typically showeterogeneous enhancement. The surrounding soft tissue, sub-
utaneous tissue and skin may be infiltrated. These are theeatures of a high-grade carcinoma [14,15]. On dynamic MRI,alignant tumours are shown to exhibit early enhancement and
low washout. [16]

ig. 7. Grey-scale ultrasound of the parotid gland shows diffuse lymphomatousnvolvement. Note the diffuse, heterogeneous echopattern with focal nodularattern. Note that the appearance is remarkable similar to sialadenitis.

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Radiology 66 (2008) 419–436 423

.1.2. Low grade carcinomaA low grade malignant lesion generally has imaging fea-

ures overlapping a benign salivary gland tumour. They areell defined with low T1W and high T2W internal signal,

imulating its benign counterpart [15,17]. This is believedo relate to the higher amount of serous and mucoid con-ent in low-grade and benign tumours compared to high-gradeggressive tumours [14,15]. Hemorrhage, fibrosis and pro-

ig. 8. (a) Grey-scale ultrasound of the parotid gland, showing a large, hypoe-hoic, heterogeneous mass (arrows) in a patient with secondary lymphoma ofhe parotid gland. Arrowhead identifies the mandibular ramus. (b) Correspond-ng axial T1W MR shows the typical homogenous, intermediate signal intensity

ass involving the superficial and deep lobes of the parotid gland.

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Fig. 9. (a) Grey-scale ultrasound shows an ill-defined, hypoechoic mass(arrows) in the apex of the parotid gland in a patient with a previous history ofnasopharyngeal carcinoma (NPC). The intra-parotid nodule is at the known siteof intra-parotid node and was confirmed to be a metastasis. Note the adjacent


heterogeneous appearance (on MR and CT) simulatingalignancy.

.1.3. Peri-neural spreadAll malignant salivary gland carcinoma have a propensity to

pread via peri-neural route. This is particularly common fordenoid cystic carcinomas. The features of peri-neural spreadnclude replacement of fat in neural foramen and diffuse or nodu-ar thickened nerve with enhancement. These features are besteen on MRI. Enlargement of neural foramen as seen on CT areate features. Discontinuous neural invasion may result in skipesions [18–20].

.1.4. Regional lymph node metastasisThe incidence of lymph node metastasis varies with his-

ological type but may be as high as 53% overall [21]. Annlarged lymph node at the known drainage site of a salivaryland tumour site should raise the suspicion of nodal metastasis.nternal heterogeneous appearance, necrosis and extra-capsularpread are the features of malignant adenopathy. The presencef nodal metastasis worsens the prognosis [22,23]. Facial nervenvolvement and tumour grade are the best predictors of nodal

etastases [22].

.1.5. MR spectroscopyA recent study suggests that MR spectroscopy may differ-

ntiate malignant and benign salivary gland tumours as wells distinguishing Warthin’s tumour from pleomorphic adenoma24]. However, its role in routine clinical practice is not wellstablished.

.2. Ultrasound features

A malignant salivary gland tumour typically shows ill-efined border with heterogeneous architecture, internalecrosis and cystic change. Doppler shows tumour hypervas-ularity with an RI > 0.8 and a PI > 2 [25] (Figs. 4–6). Localnvasion may be seen, particularly of the subcutaneous tissuend skin. Malignant nodes are identified by round shape, het-rogeneity, loss of hilar architecture, abnormal, disorganizedascularity with or without internal necrosis, cystic change andxtra-capsular spread. Cytological evidence is obtained at theame time by combining it with a FNAC. Deep tissue exten-ion, peri-neural spread and bony invasion cannot be evaluatedn ultrasound.

. Malignant salivary gland tumours

.1. Mucoepidermoid carcinoma

Mucoepidermoid carcinoma is a malignant epithelial salivaryland neoplasm arising from ductal epithelium. It is seen inll age groups, majority are the 35–65 years old, with no sex
redominance. 50% of these arise in the parotid gland and 45%n minor salivary glands in the palate and buccal mucosa [4,26].t is the most common malignancy of the parotid gland and theecond most common malignancy of the submandibular gland in
tumour (arrowheads) in the soft tissue of the neck, is also due to recurrence ofNPC. (b) Gadolinium enhanced axial T1W MR shows the intra-parotid nodalmetastases (arrows) and tumour (arrowheads) in soft tissue of the posteriorneck. Note: MR better delineates the metastases and at the same time canevaluate the primary site.

nal of Radiology 66 (2008) 419–436 425

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dult. There is a known causal relation with radiation exposure,ith a latency period of 7–32 years [6].It is classified as low-grade, intermediate-grade and high-

rade lesions histology, which correlates well with prognosis27]. Low-grade lesions appear and behave like a benign tumour.igh-grade tumours show typical malignant features, high inci-ence of local recurrence (78%) and poor prognosis (27% with0-year-survival rate) [6].

.2. Adenoid cystic carcinoma

Adenoid cystic carcinoma arises from peripheral parotiducts. It is the second most common major salivary gland malig-ancy and the most common malignancy in the submandibularnd sublingual glands.

It is seen in adults, majority in 55–75 years old. It occursost commonly in the parotid gland. The proportion is higher

n smaller salivary glands, accounts for 2–6% of parotid glandumours, 12% of submandibular gland tumours, 15% of sublin-

ig. 10. Axial T1W MR showing multiple nodules (arrows) in the soft tis-ue of the submandibular region in a patient with a high-grade submandibulararcinoma. MR is the investigation of choice to evaluate malignant salivaryesions.

Fig. 11. Grey-scale ultrasound shows a well-defined, solid, hypoechoic mass(arrow) with homogenous internal architecture and posterior enhancement.Teh

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he appearances are of a pleomorphic adenoma, however, low-grade muco-pidermoid carcinoma may closely mimic these appearances (often haseterogeneous architecture, with or without cystic change).

ual gland tumours and 30% of minor salivary gland tumours4,26,28].

It is classified into low- and high-grade lesions with featuresimulating benign tumour and aggressive tumour, respectively.

It has the greatest propensity of perineural spread amongstll head and neck tumours. The facial nerve is most commonly
nvolved, which explains the relatively high incidence of tumourain (33%) and facial nerve paralysis [29]. Late recurrence canccur up to 20 years after diagnosis and treatment [29].
ig. 12. Axial grey-scale ultrasound shows a well-defined, hypoechoic,omogenous, non-calcified mass (arrows) with posterior enhancement in theubmandibular gland. Although the mass produces a bulge in the gland, there iso extra-glandular infiltration.

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.3. Acinic cell carcinoma

Acinic cell carcinoma represents only 2–4% of all major sali-ary gland tumours. However, it is the second most commonalignant parotid tumour as most (80–90%) occur in the parotid

land. Majority of the cases are seen in middle-aged patients butt is also the second most frequent pediatric malignant salivaryland tumour [22,30].

The imaging features of this tumour are non-specific and theajority appear similar to a pleomorphic adenoma on CT and
RI.
In contrast to other malignant salivary gland tumours, theseesions may be multifocal with 3% showing bilateral parotidland involvement. Together with the non-specific imaging fea-

ig. 13. Corresponding coronal T2W (a) and post gadolinium fat suppressed1W (b) MR shows that the pleomorphic adenoma (arrow) is hyperintense on2W and shows enhancement following gadolinium injection.

Fig. 14. Longitudinal grey-scale ultrasound shows a solid, hypoechoic fairlywell-defined pleomorphic adenoma (arrow) with a focal area of dense shadow-ii

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ng calcification (arrowhead), calcification in a pleomorphic adenoma usuallyndicates chronicity of the lesion.

ures, it is easily confused with benign salivary gland tumours onmaging alone, and the diagnosis is often established on FNACr surgery.

.4. Carcinoma-ex-pleomorphic adenoma

Carcinoma-ex-pleomorphic adenoma occurs in patients withpre-existing pleomorphic adenoma or those who have had

ig. 15. Gadolinium enhanced, fat suppressed coronal T1W MR showingntense enhancement of the pleomorphic adenoma (arrow) in the superficialobe.

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resection for pleomorphic adenoma in the past. It is usu-lly seen in patients in the 6–8 decades age group. Thencidence of malignant degeneration increases from 1.5% to.5% in adenomas of less than 5 years to that of morehan 15 years [31]. The malignant component is usuallydenocarcinoma.

The patient typically presents with recent rapid enlargementf a long-standing slow-growing tumour. Associated pain, facialerve paralysis and fixation to skin reinforce the suspicion ofalignant transformation. Lymph node metastases occur in 25%

f these patients at presentation [23].The main imaging feature to suggest malignant transforma-

ion is an irregular, infiltrative margin with or without associatedalignant lymph node. Heterogenous internal signal is com-only seen in large pleomorphic adenomas due to necrosis

nd hemorrhage and is not a definite distinguishing feature
23]. T1W and T2W low to intermediate signal and gadolin-um enhanced areas may represent solid malignant component,brosis, granulation tissue or unusual appearance of a benign
umour.

ig. 16. Grey-scale ultrasound (a) shows a well-defined, hypoechoic, heteroge-eous mass (arrows) in the area of the parotid gland. Doppler (b) demonstratesascularity reminiscent of hilar vessel in a lymph node. The location and appear-nce are of a Warthin’s tumour, FNAC readily confirms its nature.

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Radiology 66 (2008) 419–436 427

.5. Lymphoma

Both primary and secondary lymphomas of the salivary glandre rare.

Primary lymphoma is classified as mucosa-associated lym-hoid tissue (MALT) lymphomas. It is more common in patientsith autoimmune disease, particularly Sojgren’s [30] disease

nd rheumatoid arthritis and in patients on immunosuppressant.0% of these occur in the parotid gland while the remaining 20%nvolves submandibular gland [23].

Secondary salivary gland lymphomas are seen in 1–8% ofatients with systemic lymphoma with 80% involving parotidland.

Salivary gland lymphoma can occur as nodal and/orarenchymal involvement.

On CT and MRI, nodal involvement is seen as multiple well-efined masses, homogenously hypodense/intermediate signaln all sequences. Parenchymal involvement is seen as diffuse
nfiltration or masses with infiltrative borders, which may beonfused with sialadenitis or other malignant salivary glandumours.
ig. 17. Grey-scale ultrasound shows a parotid Warthin’s tumour with ‘cystic’arrow) and ‘solid’ (arrowhead) components.

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It is the commonest salivary gland neoplasm regardless ofsize of the involved gland. It accounts for 60–80% of all benigntumours of major salivary glands [32]. It is usually seen in

ig. 18. Corresponding axial T2W MR shows the hyperintense cystic compo-ent, intermediate signal solid component (arrow) and nodularity of the wallarrowhead). Aspiration often yields either pale or haemorrhagic fluid.

On ultrasound, involved nodes are seen as enlarged, ovoidr lobulated lymph nodes with ‘reticulated’ pattern, ‘microcys-ic’ appearances and ‘through transmission’ [7] and exaggeratedentral vascularity (Figs. 7 and 8).

Parenchyma involvement is seen as diffuse heterogeneouscho pattern (mimicking sialadenitis) or hypoechoic, hypervas-ular mass(es) with irregular and ill-defined borders.

ig. 19. Axial grey scale ultrasound of an oncocytoma (arrow) shows it to befairly well-defined, hypoechoic, ‘solid’ mass with posterior enhancement.otice its appearance mimics a pleomorphic adenoma. Arrowhead identifies

he mandibular ramus.

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f Radiology 66 (2008) 419–436

The presence of associated extra-glandular lymphadenopathyelps to identify lymphomatous involvement.

.6. Salivary gland metastasis (Figs. 9 and 10)

Nodal metastasis is seen in parotid glands due to the pres-nce of intra-parotid. They are the first order nodes for drainagef anterior face, lateral scalp and the external auditory mea-us. That explains why malignant melanoma and squamous cellarcinomas are the most common primary.

The metastatic nodes are often seen as multiple well/ill-efined nodules, which are non-specific in appearance [5]Figs. 9 and 10). The multiplicity and interval growth with orithout a know primary should raise suspicion of malignanteposits. A guided FNAC readily confirm the diagnosis.

. Benign salivary gland tumours

.1. Pleomorphic adenoma (Figs. 11–14)

Pleomorphic adenoma is a benign, mixed salivary glandeoplasm comprising combination of epithelial and myothelial

ig. 20. Gadolinium enhanced, axial, fat suppressed T1W MR shows the onco-ytoma (arrows) as an ill-defined heterogeneous mass with thick, ill-definedim-enhancing walls, resembling a malignant lesion. Oncocytomas on imagingay mimic both benign and malignant lesion and the diagnosis is usually made

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Malignant transformation increases with chronicity, 9.5% inadenomas present over 15 [31]. Ill-defined, infiltrative border orlocal invasion should raise the suspicion of malignant change.

ig. 21. Coronal fat suppressed T2W MR shows the hemangioma as a hyperin-ense mass (arrow) involving superficial and deep lobes of the parotid gland.

dults over 40 years of age with female predominance. 90%nvolve superficial lobe of parotid, rendering ultrasound the ideal

odality for assessment. Majority of the lesions are solitary, andrimary multiplicity is seen in 5% [32].

On ultrasound, it is well-defined and hypoechoic with
obulated or bosselated surface, ‘through transmission’ andntra-tumoral vascularity [5] (Figs. 11–13), Cystic change andemorrhage are often seen in larger tumours (>3 cm). Dystrophic
ig. 22. Axial gadolinium enhanced T1W with fat suppression shows diffuse,ntense enhancement of the hemangioma (arrows) and its anatomical extent.

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Radiology 66 (2008) 419–436 429

alcification (Fig. 14) may be seen occasionally in long standingumour [7]

On CT and MRI, it is seen as well-defined, spherical or lobu-ated, homogenous mass, hyperdense than the parotid gland onT and homogenously T1W hypo- and T2W hyperintense onR (Fig. 15). Heterogenicity is seen if cystic change, hemor-

hage or dystrophic calcification is present.

ig. 23. (a) Axial grey-scale ultrasound shows a solid, hypoechoic, well-ircumscribed mass (arrows) involving superficial and deep lobes of the parotidland. (b) Power Doppler ultrasound shows marked vascularity within the mass,onsistent with hemangioma.

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eterogenicity may be due to hemorrhage, cystic change, calci-cation or malignant transformation.

.2. Warthin’s tumour

Warthin’s tumour is the second most common benign parotideoplasm, accounting for 6–10% of parotid tumours [5]. It arisesrom heterotophic salivary gland tissues in intra-parotid nodes.

ig. 24. Axial T1W MR shows a typical, well-defined, intra-parotid lipomaarrows) (a), hyperintense on T1W and fully suppressed on fat suppressionequence (b).

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It is typically seen in the tail of parotid and involvementf other salivary gland is uncommon. Multiplicity or bilateralnvolvement is seen in up to 15%. Warthin’s tumour used to beonsidered as a tumour of males. However, it is now known to beelated to smoking and ionizing radiation, explaining the recenteports of equal sex incidence [23] of these tumours.

On ultrasound, it is seen as a well-defined, heterogeneousypoechoic mass with solid and cystic component, ‘throughransmission’, central or vascularity. Multiseptated cystic archi-ecture is classical appearance but not seen in all cases [5]. Somef the tumours appear as well-defined homogenous hypoechoicass with ‘through transmission’, similar to a pleomorphic ade-

oma. Contrary to pleomorphic adenoma, Warthin’s tumouray be treated expectantly. Confirmation by FNAC may there-

ore avoid surgery. Malignant transformation (carcinoma andymphoma) are reported, but rarely (Figs. 16–18).

On CT and MRI, it is seen as a well defined, ovoid or lobu-ated mass, hypodense on CT and T1W hypointense and T2Wyperintense on MR. Cystic areas and septated architecture isetter shown on MR. Post contrast studies reveal homogenousr heterogeneous enhancement, depending on the combinationf solid and cystic component.

.3. Oncocytoma

Oncocytoma is a rare benign epithelial tumour of salivary
land, 78% occur in the parotid gland and 9% occur in the sub-andibular gland. It is typically seen in older adults of over 60
ears [31]. Malignant varieties are occasionally reported [23]f this otherwise benign entity. The imaging features are non-

ig. 25. Axial grey-scale ultrasound shows well-defined, hypoechoic massarrows) in the superficial lobe of the parotid with a ‘striated/feathery’ internalchopattern. The appearances are typical of a lipoma.


Fig. 26. Axial grey scale ultrasound shows an ill-defined, heterogeneous, thick-walled abscess (arrow) in the superficial lobe of the parotid gland, in a patientwith fever, increased white cell count and local tender mass. Arrowhead identifiesthe mandibular ramus.

Fig. 27. Axial CECT shows the abscess (arrow) as low attenuation mass withsurrounding rim enhancement.

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Radiology 66 (2008) 419–436 431

pecific, similar to other benign or low-grade malignant lesions5,23]. The diagnosis is usually established by biopsy or follow-ng surgery (Figs. 19 and 20).

.4. Infantile hemangioma

Benign epithelial tumour arising in infancy characterizedy proliferative and involutional phases. It is a true vascu-ar neoplasm and not a malformation. The proliferative phaselateaus by 1 year and the involutional phase lesions resolvey 9 years. Treatment is reserved for organ and life threateningesions.

On MR, it is seen as an intense, uniformly enhancing massith vascular flow voids and T2 hyperintensity (Figs. 21 and 22).On ultrasound, it is usually seen as a solid and hypoechoic

ass diffusely involving the parotid gland with marked intratu-oral vascularity (Fig. 23).

.5. Lipoma

Lipoma comprises 10% of all parotid tumours [31]. OnT and MRI, it is seen as a well-defined lesion with lobu-

ig. 28. Grey-scale ultrasound (a) of the submandibular gland shows it isiffusely hyypoechoic, with a heterogeneous echopattern. Note: there is no dis-lacement of mass effect on the intra-glandular vascularity on Doppler (b). Theppearances are typical of Kuttner tumour, frequently with bilateral submandibu-ar involvement. It may also involve the parotid gland to a lesser degree.

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8.3. Kimura disease

Kimura disease is a chronic inflammatory condition predom-inantly affecting young Asian male patients. It is characterized


ated contour and homogenous internal fat signal (Fig. 24). Onltrasound, it is hypoechoic relative to the surrounding parotidarenchyma with linear hyperechoic striation and is compress-ble [33] (Fig. 25). Infiltrating lipomas comprise less than 10%f the cases, with ill-defined borders on imaging. Internal het-rogenous signal with enhancing solid component should raisehe suspicion of liposarcoma.

. Other salivary ‘masses’

.1. Abscess

Salivary gland abscess can occur due to primary infection,econdary to ductal obstruction or as superimposed infection inre-existing tumour. The patients are usually febrile, with localenderness and raised WCC.

On ultrasound, it is seen as heterogenous ill-defined arear ‘mass’ with necrosis and increased vascularity in adjacentissues. On CT/MR, they appear as a heterogenous mass withecrosis and thick rim enhancement (Figs. 26 and 27).

.2. Kuttner tumour

Kuttner tumour is a pseudotumour (chronic sclerosingialadenitis of the submandibular glands) predominantly seen indult female patients. They are firm on palpation and are there-
ore easily mistaken as ‘tumour’ on clinical examination andometimes referred to as cirrhosis of the submandibular gland.n ultrasound, it is seen as well-defined, hypoechoic area involv-
ng part of one or both submandibular glands with geographical

ig. 29. Grey-scale ultrasound of the parotid gland in a patient with Kimuraisease. Note the solid, hypoechoic mass (arrows) and associated heterogenicityn the adjacent salivary tissue. Kimura may involve glandular parenchyma, intra-arotid node and adjacent subcutaneous soft tissue.

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f Radiology 66 (2008) 419–436

attern and rounded contour. Doppler reveals hypervascular-ty of the involved areas without vascular displacement [34].he characteristic sonographic appearances usually suffice toupport the diagnosis without the need of an FNAC (Fig. 28).t may also involve the parotid gland but usually to a lesseregree.

ig. 30. Corresponding post gadolinium T1W axial (a) MR shows the heteron-eneous enhancement of the mass (arrows) with heterogeneous surroundinglandular parenchyma and associated deposits in the soft tissue of the neckarrowhead). Coronal fat suppressed image (b) shows the involvement better.


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omthe soft tissue around the region of the salivary glands shouldalert the sinologist to the possibility of Kimura disease [35](Figs. 29 and 30).

ig. 31. Grey-scale ultrasound shows multiple cysts of varying sizes seen scat-ered diffusely within the parotid gland.

y unilateral, painless, slowly enlarging lymphadenopathy often
ffecting the neck.
On ultrasound, the nodal masses are seen as solid, hypoechoicnd heterogenous masses within the parotid glands, at the site

ig. 32. Coronal T2W MR shows the typical appearance, diffuse involvementf both parotid glands by multiple, hyperintense cysts.

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Radiology 66 (2008) 419–436 433

f known intra-parotid nodes. The adjacent parotid parenchymaay be heterogenous in appearance. The presence of nodules in

ig. 33. Grey-scale ultrasound of the submandibular (a) and parotid (b) glandhows diffuse involvement of the gland by macrocysts, a features of Sjogren’syndrome. The diagnosis of Sjogren’s is made clinically and on biopsy. The mainole of imaging is surveillance for lymphomatous change in Sjogren’s disease.

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Sjogren’s syndrome is an autoimmune disorder affectingadult female patients, most commonly at post-menopausal age(50–70 years old).


Heterogenous parenchyma, enhancing salivary and soft tissueodules in the vicinity of the salivary glands are the diagnosticeatures on MR/CT. [36]

.4. Benign lymphoepithelial lesion

Benign lymphoepithelial lesion are characterized by bilateralultiple lymphoepithelial cysts of salivary glands in HIV pos-

tive patients. It is seen in 5% of HIV positive patients of anyge, mainly involving the parotid glands. Submandibular andublingual glands are rarely involved.

On imaging, the involved glands are diffusely enlargedith multiple cystic and solid lesions ranging from simple

ysts to mixed cystic and solid lesions with predominantolid component. The cysts are of variable size, typicallyanging from a few milimetre to 3.5 cm in diameter. Solid
esions are seen as ill-defined masses representing lymphoidggregates and may resemble salivary gland tumours [37]Figs. 31 and 32).
ig. 34. (a) Axial grey-scale ultrasound of a VVM in the superficial parotidhows multiple, serpingenous, sinusoidal, low/anechoic structures (arrows)esembling a cluster of vessels. (b) Power Doppler ultrasound does not showignificant vascularity within the ‘venous’ channels. This is extremely commons flow within these structures is very sluggish and is better appreciated on realime grey-scale imaging than on Doppler.

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f Radiology 66 (2008) 419–436

Multiple reactive cervical adenopathy and tonsilar hyperpla-ia are associated features supporting the diagnosis.

.5. Sjogren’s syndrome

ig. 35. Axial fat suppressed T2W MR (a) and gadlinium enhancement T1WR (b) show the VVM to be hyperintense on T2W scans with variable het-

rogeneous enhancement following gadolinium injection. Although ultrasoundeadily identifies the nature of the lesions, MR is better in delineation of itsxtend, multiplicity and osseous involvement.

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In early phase, the involved salivary glands may be normaln size or diffusely enlarged with normal parenchymal pattern.

In intermediate phase, the salivary glands are diffuselynlarged with multiple, scattered cysts and solid masses repre-enting parenchymal destruction and lymphoid aggregates [38].he cysts are typically similar in sizes, ranging from <1 mm

microccysts) to macrocysts and mixed solid-cystic masses2 cm scattered throughout the glands and the parenchymalchopattern may be reticulated [39]. The solid lesions may sim-late salivary gland tumour (Fig. 33).

In chronic phase, there is an atrophy of the glands with hypoe-hoic echo pattern [40,41].

The appearances at the intermediate phase may exactly mimicLL but tonsilar hyperplasia and reactive cervical lymph nodesre usually not a feature.

The diagnosis of Sjogren’s is usually suggested clinically andonfirmed by a biopsy. The role of imaging is predominantlys a surveillance tool as patients with Sjogren’s syndrome aret a higher risk (44 times) of developing salivary lymphomas30].

.6. Venous vascular malformation

Venous vascular malformations are slow-flow post-capillaryesion composed of endothelial-lined vascular sinusoids. It is the

ost common vascular malformation of the head and neck andhe masseter and parotid are often involved.

It is seen as lobulated and transpatial soft tissue masses withhleboliths [42]. Vascular flow is slow, which is seen only as arey-scale movement on ultrasound without Doppler flow signal44]. The enhancement pattern on CR and MRI varies, may beatchy and delayed or homogenous and intense, related to theize of vascular channel [43].

Although ultrasound readily establishes the diagnosis,T/MR may be necessary to evaluate their anatomical extent,ultiplicity and osseous involvement if any (Figs. 34 and 35).

. Conclusion

Salivary gland tumours are a common clinical dilemma andmaging plays a useful role in establishing diagnosis, evaluatingxtent of local and distant involvement.

Ultrasound is the ideal initial investigation for evaluating sub-andibular masses and lesions in the superficial lobe of parotid,

articularly as it is readily combined with FNAC.However, MR is the imaging modality of choice in evaluating

alignant salivary lesions in the head and neck.

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Imaging of Salivary Glands Tumours

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