Multimodality Imaging of Pediatric Parotid Gland Lesions 1

A wide spectrum of inflammatory diseases, includingsialolithiasis, neoplasms and developmental disordersmay be encountered in the pediatric parotid gland.These lesions may present with swelling of the parotidregion, which makes diagnosis problematic. The use ofimaging plays an important role in defining the locationand extent of lesions and for evaluating involvement ofthe facial nerve, including the mastoid portion. Finally,

imaging can provide a specific diagnosis in a proper clin-ical setting. The imaging modalities used to evaluateparotid lesions have changed over the past severaldecades. Plain films and sialograms were used initially,but basic approaches today involve ultrasonography(US), computed tomography (CT) and magnetic reso-nance imaging (MRI) (1). In this review, we describe theimaging spectrum of a variety of congenital and ac-quired lesions in the pediatric parotid gland, with a com-parison of the findings with the use of various imagingmodalities.

Normal Gland Anatomy and Imaging Considerations

The parotid gland is the largest of the three paired sali-

J Korean Radiol Soc 2008;59:115-129

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Multimodality Imaging of Pediatric Parotid Gland Lesions1

Yoo Na Kim, M.D., So-Young Yoo, M.D., Ji Hye Kim, M.D., Eo Hong, M.D.

1Department of Radiology, Samsung Medical Center, SungkyunkwanUniversity School of MedicineReceived March 25, 2008 ; Accepted June 18, 2008Address reprint requests to : So-Young Yoo, M.D., Department ofRadiology, Samsung Medical Center, Sungkyunkwan University Schoolof Medicine, 50, Ilwon-dong, Kangnam-gu, Seoul 135-710, Korea. Tel. 82-2-3410-6417 Fax. 82-2-3410-2559 E-mail: [email protected]

Although diseases of the parotid gland are relatively uncommon in children, a vari-ety of benign and malignant lesions may occur and the use of imaging is essential foraccurate diagnosis and treatment. Ultrasonography (US) is the initial imaging modalityutilized for suspected parotid lesions, and its use may suggest a correct diagnosis in anadequate clinical setting. The use of computed tomography (CT) and magnetic reso-nance imaging (MRI) are useful for the assessment of large and atypical lesions. Thesemodalities also allow the ability to image the deep parotid lobe and to better define thenature of a lesion. CT is the preferred imaging modality for inflammatory processes,including suspected sialolithiasis, abscesses and salivary duct obstructions, whereasMRI is usually used to evaluate tumors due to excellent anatomic resolution and a lackof ionizing radiation exposure, especially in children. This report describes the imagingfindings of various parotid gland lesions in children. Familiarity with these findingswill aid in lesion characterization and should facilitate optimal clinical management.

Index words : Parotid glandChildUltrasonographyX-Ray TomographyMagnetic resonance (MR)

vary glands, which arises as an epithelial invagination inthe lining of the oral cavity. It is located at the angle ofthe mandible, and is bounded by the ramus of themandible and masseter muscle anteriorly, and by themastoid process and sternocleidomastoid muscle poste-riorly. The gland is divided into the larger superficial(lateral) and smaller deep (medial) lobe by the facial

nerve that enters the posterior gland, branches, andthen exits the gland anteriorly (Fig. 1).

US is a fast, non-invasive modality that provides excel-lent resolution of superficial structures, and is generallyregarded as the initial imaging tool of choice for the eval-uation of suspected parotid lesions (2). US is usually per-formed with a linear transducer with a frequency of 5-12 MHz. As depicted on US, the normal parotid gland ishomogenous and hyperechoic relative to the adjacentmuscle (Fig. 2). Intraglandular lymph nodes, which areusually hypoechoic and less than 5-6 mm in size, canbe seen in asymptomatic children (2, 3).

As depicted on color Doppler US, the gland parenchy-ma is not hypervascular and produces minimal flow sig-nals. The course of the facial nerve, which is not readilyvisualized on US, can be inferred by the identification ofthe retromandibular vein within the gland, as the nervelies just lateral to this vessel. The deep lobe of theparotid gland is not usually well demonstrated on US,and thus, there are advantages to the use of CT and MRIin terms of imaging deep or large lesions.

CT is particularly useful for the detection of sialolithia-sis and bone destruction, and for the evaluation of ex-tensions of inflammatory or neoplastic diseases out ofthe parotid capsule. In children, CT attenuation of theparotid gland may be similar to that of muscle due tolower glandular fat levels. It is one of the limitations ofthe use of CT in children. Progressive fatty infiltrationoccurs in the gland with age and the gland shows less at-tenuation than muscle. The use of MRI is preferable toCT for the imaging of parotid masses, especially whenassociated with facial nerve symptoms, as MRI canidentify the facial nerve, and is the most useful modality

Yoo Na Kim, et al : Multimodality Imaging of Pediatric Parotid Gland Lesions

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Fig. 1. The normal parotid gland in a 10-year-old girl. An axialT1-weighted MR image shows the parotid gland (P) andparotid duct (thick black arrows) piercing the buccinator mus-cle (B) just lateral to the second maxillary molar. Note the me-dial external carotid artery (thin white arrow) and more lateralretromandibular vein (thin black arrow). A branch of intra-parotid facial nerve (thick white arrow) is seen projecting later-ally around the lateral margin of the retromandibular vein. M = masseter muscle

A BFig. 2. A normal parotid gland in a 6-year-old boy. (A) Transverse and (B) longitudinal US images show a homogenous, hypere-chogenic parotid gland at the angle of the mandible. The normal anatomy of the right parotid gland is as follows: P = parotid gland,v = retromandibular vein, a = external carotid artery, M = echogenic surface of the mandible, Ma = masseter muscle.

for the evaluation of tumor extent. The signal intensityof the parotid gland is dependent on fat content; andnerves and ducts have lower signal intensity. The use offat saturation is helpful for contrast-enhanced imaging.

Sialography is rarely used currently because of the in-vasive nature of the modality and the current capabili-ties of CT and MRI. It is performed by injecting contrastmaterial into the ductal system via the oral opening ofthe parotid (Stensen’s) duct that exits the anteromedialportion of the gland, crosses the masseter superficially,pierces the buccinator, and enters the oral cavity oppo-site the second maxillary molar. The procedure is indi-cated as follows: to detect small sialoliths or foreign bod-ies, assess the extent of irreversible duct damage due toinfection, and evaluate fistulas, strictures, diverticulaand ductal trauma. However, clinically active infectionscontraindicate the use of the procedure, as it is likely tocause the spread of infection into the gland in a retro-grade manner.

Inflammatory Disorders

Acute Parotitis

Parotitis is the most common parotid disease in chil-dren. Acute parotitis manifests as a unilateral or bilater-al painful swelling at the angle of the mandible. In gen-eral, it has a viral origin, often secondary to mumps,whereas Staphylococcus aureus is the most commoncause of bacterial parotitis. Staphylococcal infection usu-ally affects premature babies or immunosuppressed chil-dren (2, 4, 5). As depicted on US, the affected glandshows diffuse enlargement with heterogenousechogenicity, and may demonstrate multiple, small hy-poechoic nodules, representing enlarged intraparotidlymph nodes, small abscesses or dilated ducts (5) (Fig.3A). Color Doppler US shows increased intraparotidblood flow (Fig. 3B) and contrast-enhanced CT shows anenlarged gland with diffuse enhancement and fat strand-ing around the gland (Fig. 3C). In severe cases, abscess


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A B

Fig. 4. A parotid abscess in a 7-year-oldboy. A. A longitudinal US image of the rightparotid gland shows a low echoic mass(arrows). B. An axial contrast-enhanced CT scandemonstrates an enhancing mass le-sion (arrows) with an inner low atten-uated area in the right parotid glandthat also shows mild diffuse enhance-ment with swelling, indicating inflam-mation.

A B CFig. 3. Acute parotitis in a 4-year-old girl. A. A transverse US image of the left parotid gland shows diffuse swelling with inner multiple low echoic nodules. B. Color Doppler US shows increased parenchymal vascularity. C. An axial contrast-enhanced CT scan shows enlargement of the left parotid gland with heterogenous enhancement (arrows) ascompared with the normal right side.

formation may occur, which appears as a hypoattenuat-ed focus with peripheral enhancement (Fig. 4).

Chronic Recurrent Parotitis

Chronic recurrent parotitis is defined as a recurrentparotid inflammation, generally associated with non-ob-structive sialectasis (6). Although it is a rare condition ofunknown etiology, it is the most commonly encoun-tered inflammatory salivary gland disorder in childrenafter the mumps. Typical clinical features are intermit-tent unilateral or bilateral swelling of the parotid glandaccompanied by pain, fever and malaise, and it is usual-ly self-limiting and resolves by adolescence. Chronic re-current parotitis may be associated with Sjogren’s dis-ease, human immunodeficiency virus infection, and im-mune deficiencies, such as hypogammaglobulinemia.Occasionally, chronic recurrent parotitis may be also beassociated with ductal obstruction by a stone.

US depicts the presence of a heterogenous gland withmultiple small hypoechoic or punctuate echogenic areas(Fig. 5). These hypoechoic areas are thought to representboth ectatic ducts and surrounding lymphocyte infiltra-tion. The punctate echogenic foci may correspond to mu-cus or calcification within the dilated ducts (7). The useof sialography demonstrates multiple, sharply demarcat-ed, and small round areas of contrast collection, whichare equivalent to the hypoechoic areas noted on US.

Sjogren’s Syndrome

Sjogren’s syndrome, which occurs rarely in childhood,is an autoimmune disorder characterized by chronic

lymphocytic infiltration of the salivary and lacrimalglands, and usually presents as recurrent parotidswelling. As the disease progresses, glandular enlarge-ment appears with denser attenuation than normal asseen on CT. Advanced Sjogren’s syndrome shows USfindings similar to those of chronic recurrent parotitisand a gland with a “salt and pepper” or “honeycomb” ap-pearance on CT and MRI (Fig. 6A, B) (1, 4). During theearly stage of the disease, the use of sialography demon-strates innumerable peripheral punctate collections ofcontrast material, and as the disease progresses, thesecollections of contrast material become larger, and even-tually the gland is destroyed (Fig. 6C). Sjogren’s syn-


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A B CFig. 6. Sjogren’s syndrome in a 15-year-old-girl with recurrent swelling at bilateral parotid areas. An axial contrast-enhanced CTscan (A) and axial T2-weighted MR image (B) show diffuse enlargement of both parotid glands with increased attenuation and sig-nal intensity, respectively (arrows). Note the presence of the multiple microcystic low attenuating lesions on the CT image andmultiple punctate low signal intensity areas on the MR image throughout both parotid glands. A lateral view of a parotid sialogram(C) shows multiple punctate collections of contrast material evenly scattered throughout the gland. The central duct system seemsto be normal.

Fig. 5. Chronic recurrent parotitis in a 4-year-old girl who hadrecurrent swelling at the parotid area. A longitudinal US imageof the right parotid gland shows mild enlargement with het-erogenous echogenecity and multiple low echoic areas.

drome has a high associated risk of parotid lymphomadevelopment and the development of other lymphopro-liferative diseases. Thus, follow-up monitoring of pa-tients is important (8).

Sialolithiasis

Salivary calculi are typically associated with recurrentpainful swelling of the parotid during eating and can beaccompanied by bacterial infection. About 10-20% ofsalivary calculi occur in the parotid gland (5).Sialolithiasis has been reported to be associated withcystic fibrosis, but it can also arise as an isolated finding(7). Although 60% of parotid stones are radiopaque, theymay be difficult to visualize on plain radiographs due tothe superimposition of bony structures (1, 5, 7).Sialography is a highly accurate technique for the diag-nosis of sialolithiasis, but is somewhat invasive (Fig. 7A).US is the initial imaging method to utilize in cases withclinically suspected parotid calculi, which are demon-strated as hyperechoic foci with acoustic shadowing as-sociated with sialectasis and inflammatory changes. CTis generally performed without contrast as under suchcircumstances, small opacified blood vessels may mimicsmall duct stones (Fig. 7B). If inflammation or an ab-scess is suspected, a contrast-enhanced scan might beuseful to perform after stones have been identified onnon-enhanced CT.

Neoplasms

Salivary gland neoplasms are uncommon in childrenand account for 1% of all pediatric tumors. Salivarygland tumors compose 8% of primary tumors of the

head and neck in children, and 90-95% of salivary tu-mors occur in the parotid gland (5). Up to 65% of pedi-atric salivary gland neoplasms are benign, and are com-monly identified as hemangiomas or pleomorphic ade-nomas (5, 7). Mucoepidermoid or acinic cell carcinomasaccount for 60% of malignant salivary gland neoplasmsin children and occur most commonly in children near10 years of age (5, 9). The remaining malignant tumorsinclude rhabdomyosarcomas, adenoid cystic carcino-mas, adenocarcinomas, lymphomas, and squamous cellcarcinomas. Rapid mass growth, facial nerve paralysis,attachment to the skin or deep tissues and lym-phadenopathy increase the possibility of a malignancy.The majority of malignant tumors are poorly circum-scribed with irregular margins. However, small or lowgrade malignant tumors may have features suggestingbenign lesions. Thus, tissue sampling is required for adefinitive diagnosis.

Hemangiomas

Hemangiomas are benign neoplasms of endothelialcells and are the most common benign salivary gland tu-mors in children. In particular, they represent 90% ofparotid tumors that occur during the first year of life (1)and have a significant female predominance (5). A he-mangioma manifests as a soft, non-tender mass shortly af-ter or at birth. Usually, they grow rapidly during the firstyear of life, reaching a peak size at 1-2 years of age (pro-liferative phase). In most cases, the lesions then sponta-neously regress and disappear completely by the time ofadolescence (involutional phase) (1, 10). Therefore,surgery may be avoided until adulthood, but can be indi-cated in cases with major complications, such as bleed-ing, compression of vital structures or coagulopathy.


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A B

Fig. 7. Sialolithiasis in an 8-year-oldgirl with preauricular painful swelling.A. In a siglogram, an ovoid filling de-fect (arrow) is seen in distal portion ofStensen’s duct. B. A precontrast CT scan shows a highdensity lesion (arrow), suggesting thepresence of a parotid duct stone.

As seen on US, hemangiomas appear as homogenoushypoechoic lesions, often with a lobulated appearance(Fig. 8A). Color Doppler US can confirm the presence ofincreased vascularity to a variable degree in the masses(Fig. 8B), and can detect the presence of feeding arteriesand draining veins. With the use of contrast-enhancedCT, hemangiomas are visualized as well-demarcatedmasses with intense homogenous enhancement. On T2-weighted images, hemangiomas typically show markedhyperintensity and signal voids representing intralesion-al or perilesional blood vessels (Fig. 9).

Pleomorphic Adenomas

A pleomorphic adenoma or benign mixed tumor is themost common benign epithelial tumor of the pediatricparotid gland (1). Typically, the tumor manifests as ahard, painless and slow-growing parotid mass. As de-picted on US, small pleomorphic adenomas appear as

oval or round, well defined and homogenously hypoe-choic masses. Large tumors have a more heterogenousappearance due to necrosis, hemorrhage, and cysticchanges, and tend to have a lobulated margin (Fig. 10)(1). On CT, calcifications or ossifications may be ob-served within this tumor. On MR images, the tumor sig-nal intensity depends on its histological components.Areas containing abundant fibromyxoid stroma appearas bright signal intensity regions on T2-weighted imagesand show marked enhancement, whereas areas of highcellularity appear as low signal intensity regions on T2-weighted images with weak enhancement (Fig. 11A, B).Malignant transformation and local recurrence aftersurgery are the major causes of morbidity and mortalityassociated with this tumor (1, 11).

Warthin’s Tumor

Warthin’s tumor or cystadenolymphoma is the second


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A B

Fig. 9. A parotid hemangioma in a 4-year-old boy. A. An axial T2-weighted MR imagewith fat suppression shows markedenlargement of the right parotid glandreplaced by a lobulating hyperintensemass (thick arrows) with internal sig-nal voids due to dilated vessels (arrow-heads). A cutaneous hemangioma is al-so noted in the vicinity (thin arrows).B. On an axial contrast-enhanced T1-weighted MR image with fat suppres-sion, the mass demonstrates intensehomogenous enhancement (arrows).

A BFig. 8. Parotid hemangioma in a one-month-old baby. A. A transverse US image of the left parotid gland shows hypoechoic echotexture with inner fine echogenic septa. B. Color Doppler US shows much increased vascularity.

most common benign neoplasm of the salivary gland inadults, but its presentation is rare in children. It usuallyoccurs in the tail of the parotid gland, and arises fromthe ectopic ductal epithelium. Multifocal tumors in oneor both parotid glands have been reported to occur in upto 10-30% of cases and are highly suggestive ofWarthin’s tumor (1, 11).

As depicted on US, a Warthin’s tumor tends to beround or oval, well-defined, hypoechoic mass, which ismore inhomogenous than a pleomorphic adenoma dueto common cyst formation, especially in the larger tu-

mors. Cystic portions within a solid lesion are consid-ered typical of a Warthin’s tumor, which may also ap-pear as a cystic mass mimicking cystic carcinomas, suchas a mucoepidermoid carcinoma or acinic cell carcino-ma. Technetium -99m scintigraphy can help to diag-nose Warthin’s tumor, as the tumor shows higher up-take of the radioisotope than the normal glandparenchyma (11). CT and MRI commonly show a well-defined, cystic or solid lesion located in the posteroinfe-rior segment of the superficial lobe of the parotid gland.Surgical resection is recommended as a Warthin’s tu-


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A

B

Fig. 10. A pleomorphic adenoma in a 14-year-old boy. A longitudinal US image (A)shows a lobulating contoured hypoechoic mass in the right parotid gland. An axial con-trast-enhanced CT scan (B) demonstrates the presence of a lobulating soft tissue mass inthe right parotid gland (arrows).

A B

Fig. 11. A pleomorphic adenoma in a19-year-old boy. A. An axial T2-weighted MR imageshows a heterogenous hyperintensemass (arrows) with lobulation involv-ing the superficial and deep lobe of theleft parotid gland. B. On an axial contrast-enhanced T1-weighted MR image, irregular periph-eral enhancement of the mass is noted(arrows).

mor may undergo malignant transformation.

Neurogenic Tumors

Neurogenic tumors including schwannomas (neurile-momas) and neurofibromas may arise from the facialnerve or its branches schwannomas are solitary, where-as neurofibromas are often multiple masses. Multiple orplexiform neurofibromas have ill-defined margins andinfiltrate surrounding tissues, and usually occur in pa-tients with neurofibromatosis type 1 (Fig. 12) (10).

Neurogenic tumors often contain cystic areas, and the

tumors are seen on CT as homogenous masses isodenseto muscle or heterogenous masses with focal areas ofcystic change with moderate or marked enhancementafter contrast administration. On MRI, this type of tu-mor tends to show low to intermediate and high signalintensity on T1-weighted images and T2-weighted im-ages, respectively (Fig. 13).

Mucoepidermoid Carcinomas

Mucoepidermoid carcinomas (MECs) are the mostcommon malignant tumors of the pediatric salivarygland (9), and are categorized histologically into threegrades: low, intermediate and high. Moreover, thesegrades correspond well with prognosis, and thus thishistological grading scheme is an important prognosticindicator.

Imaging findings also depend on tumor grade. Lowergrade MECs present as well-defined masses, mimickinga pleomorphic adenoma. High grade MECs are often illdefined with fewer cystic areas than low-grade tumorsand tend to be more homogenous as seen on CT, andare likely to appear as regions of low signal intensity onboth T1- and T2-weighted images. However, the en-hancement patterns are variable as seen on CT and MRI(Fig. 14) (1, 11).

Acinic Cell Carcinomas

Acinic cell carcinomas (ACCs) are rare salivary glandtumors in children. Nevertheless, they have been re-


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A B

Fig. 13. A neurilemmoma in a 13-year-old boy. A. An axial T2-weighted MR imageshows a well-defined mass with innercystic or necrotic areas and fluid-fluidlevel suggesting hemorrhage in the leftparotid gland (arrows). B. On an axial contrast-enhanced T1-weighted MR image, the mass is seenwith strong enhancement (arrows)with inner non-enhancing cystic ornecrotic areas.

Fig. 12. A parotid neurofibroma in a 10-year-old boy with neu-rofibromatosis type 1. On an axial contrast-enhanced CT scan,a diffuse ill-defined low attenuated lesion replaces the entireright parotid gland (white arrows). A neurofibroma is also not-ed in the right parapharyngeal space (black arrows).

ported to be the second most common parotid malig-nancy after an MEC in the pediatric population (5, 9).Imaging findings of ACCs are nonspecific (Fig. 15),though most ACCs have a benign appearance and oftensimulate a pleomorphic adenoma and Warthin’s tumor.

Rhabdomyosarcomas

A rhabdomyosarcoma is the most common pediatric

soft tissue sarcoma, and accounts for approximately halfof all soft tissue sarcomas in children. About 35-40% ofrhabdomyosarcomas occur in the head and neck and10% of these tumors involve the parotid gland (10).

As seen on US, rhabdomyosarcomas appear as het-erogenous low echoic masses with markedly increasedvascularity (Fig. 16A, B), and as seen on CT, the tumorsappear as isoattenuating heterogeneous masses relativeto muscle, with ill-defined margins (Fig. 16C).Rhabdomyosarcomas are seen with variable enhance-ment after contrast administration, and MRI also depictsthe lesions as indistinct, irregular heterogenous masses.The tumors are isointense on T1-weighted images andhyperintense on T2-weighted images with heterogenousor homogenous enhancement following contrast materi-al administration (Fig. 16D, F). Rhabdomyosarcomasusually infiltrate into the surrounding structures and di-rectly invade contiguous soft tissues and bony structures(10).

Adenoid Cystic Carcinomas

Adenoid cystic carcinomas compose 4-8% of all sali-vary gland tumors. The tumors usually occur in subjects20 to 80 years-old and are rare in patients under 20 yearsof age. Adenoid cystic carcinomas grow slowly; howev-er, late metastases are frequent. Perineural invasion istypical, and therefore pain is a relatively common symp-tom (1).

These carcinomas often appear as benign tumors withwell-defined margins. Nerve enlargement with en-hancement suggests perineural infiltration (1).


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Fig. 14. A mucoepidermoid carcinoma in a 9-year-old boy. Anaxial contrast-enhanced CT scan demonstrates a well-definedenhancing intraparotid mass (arrows) with a small focal cysticarea.

A B

Fig. 15. An acinic cell carcinoma in an11-year-old boy. A. A transverse US image shows thepresence of a relatively defined hypoe-choic solid mass in the right parotidgland (arrows). B. An axial contrast-enhanced CT scanshows a homogenously enhancingmass located in the deep lobe of theparotid gland (arrows).

Lymphoma and Leukemia

A salivary gland primary lymphoma is rare and mostcommonly involves the parotid gland. Of the differenthistological types, the mucosa-associated lymphoid tis-sue (MALT) lymphoma is the most common (12). A sec-ondary lymphoma of the salivary glands is also rare and80% of cases involve the parotid gland (1). In these cas-es, the prognosis is poor owing to lymphoma dissemina-tion. Clinically, a salivary gland lymphoma is usuallypainless and manifests only as progressive swelling ofthe salivary gland. It is usually associated with autoim-

mune disease, most frequently with Sjogren’s syn-drome. Moreover, the risk of non-Hodgkin’s lymphomain Sjogren’s syndrome is 40 times higher than the risk inthe normal population (8). Rheumatoid arthritis also oc-casionally accompanies a lymphoma and an unusual re-lationship between lymphoma development and sys-temic lupus erythematosus (SLE) treatment has been re-ported (12, 13).

Intraparotid nodal involvement of a lymphoma ap-pears as multiple, round or oval, hypoechoic lesionswith a sharp margin as depicted on US. Parenchymal in-


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A B C

D E FFig. 16. A rhabdomyosarcoma in a 4-year-old boy. A transverse US image (A) shows a lobulating contoured low echoic mass in-volving the right parotid gland (arrows) and markedly increased vascularity as seen on color Doppler US (B). An axial contrast-en-hanced CT scan (C) demonstrates the presence of an ill-defined heterogenous enhancing mass (white arrows) in the right parotidgland with prominent vascular structures and extension to the adjacent parapharyngeal and carotid space (black arrows). CoronalMR images show a large parotid mass (arrows) with T2 high and T1 low signal intensity, respectively (D, E) and strong heteroge-nous enhancement after contrast administration (F).

volvement shows diffuse infiltration with an ill-definedmargin. An enlarged gland with increased vascularitywithin the lesion is seen with a lymphoma (11). On CT,focal masses that are restricted within the intraparotidlymph nodes or diffuse infiltration present with slighthomogenous enhancement after contrast administration(Fig. 17) (1).

Leukemic involvement of the parotid gland is uncom-mon. Enlargement of the gland is associated with vari-able echogenicity and increased blood flow as seen onUS, and CT and MRI also demonstrate various attenua-tions and signal intensities, respectively. The clinical set-ting is usually important for diagnosis as it is difficult todistinguish leukemia from other parotid diseases thatpresent with an enlarged gland.

Metastases

Parotid metastases are uncommon in children. Mostprimary tumors are cutaneous malignancies of the headand neck. Squamous cell carcinomas, melanomas of thescalp or periauricular area, and thyroid carcinomas maymetastasize to the parotid gland (4, 14). Most parotidmetastases are located in the intraparotid lymph nodes.

US demonstrates multiple, well-defined, round, hy-poechoic lesions with increased vascularity, but it maybe difficult to differentiate between metastatic lesionsand other diseases, such as inflammation, infectiousgranulomatous disease, lymphoma and acute adenopa-thy. Therefore, the use of fine needle aspiration orsurgery is necessary to confirm the diagnosis in mostcases.

Vascular Malformations

The Mulliken and Glowacki classification system clas-sifies vascular lesions into two main categories: heman-giomas and vascular malformations (15). Vascular mal-formations consist of some combination of congenitallyabnormal vessels and the malformations are furthersubdivided into venous, lymphatic, capillary and arteri-ovenous malformations, depending on the predominantvessel type. MRI has been shown to be helpful for thedetermination of lesion type and extent. Vascular mal-formations tend to enlarge as children grow and do notundergo spontaneous involution. Thus, surgical treat-ment or sclerotherapy are necessary (15).

As seen on US, lymphatic malformations usually ap-pear as thin septated cystic masses with predominanthypoechoic components (Fig. 18). If hemorrhage or in-


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Fig. 17. A T-cell lymphoblastic lymphoma in a 2-year-old girl.On an axial contrast-enhanced CT scan, both parotid glandsare diffusely enlarged with homogenous enhancement (whitearrows). Multiple cervical lymph node enlargements are alsonoted (black arrows).

Fig. 18. A parotid lymphatic malforma-tion in a 13-year-old girl. US depicts amultiseptated cystic mass in the rightparotid gland (arrows).

fection is present, intralesional echogenic floating debriscan be observed. On CT and MRI, lymphatic malforma-tions are seen as cystic masses with thin septations thatfrequently infiltrate surrounding tissues. After contrastadministration, there is usually little or no enhance-ment, although an enhancing solid portion can be pre-sent within a mass. Hemorrhage occurs frequently andresults in fluid-fluid levels with variable attenuations orsignal intensities that depend on hemorrhage age at thetime of imaging (Fig. 19) (5, 10, 11).

Developmental Disorders

Congenital Agenesis of the Parotid Gland

Agenesis of the parotid gland is a rare entity. It usually

occurs alone or with first branchial arch developmentaldisorders and other congenital anomalies, such as ahemifacial microstomia, cleft palate, mandibulofacialdysostosis and anophthalmia (1). It is important to diag-nose this disease since the contralateral parotid glandmay be mistaken as an abnormal mass due to the pres-ence of facial asymmetry.

Accessory Parotid Gland

The accessory parotid gland is a nodule of normal sali-vary gland tissue that is obviously separated from themain parotid gland. The facial process of the parotidgland, which is a normal anterior extension of theparotid tissue continuing with the main gland, shouldnot be misdiagnosed as an accessory gland. Studies onhuman cadavers have determined that the incidence ofan accessory gland is approximately 20% to 40% (16).The accessory gland is located on masseter muscle adja-cent to Stensen’s duct at variable distances from themain gland, and usually drains into Stensen’s ductthrough one or more excretory ducts. A palpable massin the mid-cheek is a common manifestation, with orwithout tenderness. The accessory parotid may be asso-ciated with a benign or malignant neoplasm, benignlymphoepithelial lesions and a congenital fistula fromthe accessory parotid to the facial skin (Fig. 20) (17).

US depicts soft tissue with the same echogenicity asthe normal parotid gland, and provides the precise loca-tion of the lesion and its relationship with adjacentstructures. CT and MRI provide additional informationon the presence of a duct stone, soft tissue calcification,and the internal characteristics of abnormal lesions, es-


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Fig. 19. A parotid lymphatic malformation in a 6-year-old girl.A T2-weighted MR image with fat suppression demonstratesthe presence of a multisepatated cystic mass with multiple flu-id-fluid levels in the left parotid gland, representing a lym-phangioma with hemorrhage.

A B

Fig. 20. A congenital fistula from anectopic parotid gland in a 7-year-oldgirl. The patient had a fistulous open-ing at the facial skin near the mouthangle from birth. A. CT fistulography obtained after in-jection of water-soluble contrast intothe fistulous opening in the cheekdemonstrates a soft tissue lesion opaci-fied by contrast (arrows) at the antero-lateral aspect of the atrophic massetermuscle, which is thought to be an ec-topic parotid gland. Note the absenceof glandular tissue at the right parotidbed. The left parotid gland (L) looksnormal. B. A section taken more caudad than(A) shows opacification of the fistula(arrowheads).

pecially tumors.

Miscellaneous Lesions

Kimura Disease

Kimura disease is a rare angiolymphoproliferative dis-order of unknown etiology, which is characterized bythe presence of a lymph-folliculoid granuloma witheosinophilic infiltration in the mass and surrounding tis-sues. Kimura disease is markedly more prevalent inyoung Asian males in their second or third decades oflife (18). Its typical clinical presentation is a painless,soft-tissue mass with local lymphadenopathy. A headand neck location is most common, and the majority ofcases involves subcutaneous tissues, the major salivary

glands or regional lymph nodes. Peripheral bloodeosinophilia and an elevated serum IgE level are oftenassociated with the disorder.

US findings of Kimura disease are varied. Soft tissuemasses are well-defined or ill-defined and hypoechoicwith homogenous or heterogenous internal architecture,and although masses contain a predominant solid com-ponent, cystic or necrotic portions may also be present(18). T2 signal intensities on MRI and degrees of en-hancement are diverse and depend on the ratio of fibro-sis to vascular proliferation within a lesion. Massesdemonstrate high signal intensity of a varying degree onT2-weighted images and low to intermediate signal in-tensity on T1-weighted images (Fig. 21, 22) (19).

It is difficult to diagnose Kimura disease based solely


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A B CFig. 22. Kimura disease in a 10-year-old girl. A. An axial T2-weighted MR image shows a relatively well-circumscribed hyperintense mass (arrows) involving the right parotidgland and superficial masticatior space. B, C. On an axial T1-weighted MR image, the mass shows iso-signal intensity (arrows in B) with strong enhancement after contrastadministration (arrows in C).

Fig. 21. Kimura disease in a 10-year-old boy. An axial contrast-enhanced CT scan shows well-enhancing infiltrative soft tis-sue lesions involving the right parotid gland and periparotidarea (white arrows). Multiple enlarged lymph nodes are alsoseen in both necks (black arrows).

Fig. 23. Castleman’s disease in a 6-year-old girl. An axial con-trast-enhanced CT scan shows a well-defined mass with ho-mogenous and strong enhancement in the right parotid gland(arrows).

on radiological findings. Thus, a biopsy and considera-tion of its unique clinical features are necessary.Treatment options include surgery, administration of re-gional or systemic corticosteroids, and radiation thera-py. Although Kimura disease is a chronic benign condi-tion with an indolent course, recurrence after surgery orafter the cessation of steroid therapy is common.

Castleman’s Disease

Castleman’s disease is a rare, benign lymphoprolifera-tive disease of unknown etiology. The majority of le-sions occur within the head and neck, and salivarygland involvement is rare.

Two histologic types of Castleman’s disease have beendescribed the hyaline vascular and plasma cell types.The hyaline vascular type is usually unicentric, whereasthe plasma cell type often occurs at multiple sites andcan be associated with systemic symptoms. This multi-centric Castleman’s disease has a high risk to develop in-to a malignancy, such as lymphoma or Kaposi’s sarcoma(20).

CT and MRI findings are nonspecific, demonstrating awell-defined, homogenous mass with strong enhance-ment within the gland (Fig. 23) (20).

Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) can involve theparotid gland; however, this is extremely rare, even formultisystem LCH (21). Involved bilateral parotid glandsare homogenously enlarged as seen on CT and are asso-ciated with multiple enlarged regional cervical lymphnodes (Fig. 24) (21).

Pneumoparotid

A pneumoparotid, also known as pneumoparotitis and

pneumosialadenitis, arises from air insufflation into theparotid gland when the intraoral pressure increases dueto the following: chronic obstructive pulmonary disease,cystic fibrosis, glassblowing, horn playing, a dental pro-cedure or as habitually self-induced means by childrenor adolescents to seek attention. Anatomical abnormali-ties, such as a patulous duct, hypertrophy of the mas-seter muscle, and weakness of the buccinator musclecan also be associated with a pneumoparotid.

Clinical manifestations usually include swelling, pain,tenderness, and erythema in the parotid region. A pneu-moparotid may occur as a transient or recurrent event.In recurrent pneumoparotid cases, its course is not com-pletely benign as it may give rise to sialectasia, recurrentparotitis and even subcutaneous emphysema. CT is themost useful modality for diagnostic purposes, especiallyif there is a small amount of air in the parotid gland (Fig.25). US and MR sialography are also valuable tools.


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A B

Fig. 24. Langerhans cell histiocytosisin a 7-month-old girl. A. A US image of the parotid glandshows multiple aggravated low echoicnodules within the enlarged gland. (ar-rows). B. An axial contrast-enhanced CT scandemonstrates the presence of multipleconglomerated enhancing lesions in-volving both entire parotid glands(thick arrows). Multiple enlargedlymph nodes are also seen in bothnecks (thin arrows).

Fig. 25. A pneumoparotid in a 9-year-old-boy. An axial con-trast-enhanced CT scan shows linear air density along the bi-lateral parotid gland ducts (arrows). On a precontrast scan,there is no evidence of a parotid duct stone (not shown here).

Treatment completely depends on the cause of thepneumoparotid. In an isolated case, only reassuranceand prophylactic antibiotics are needed (22).

Summary

Although parotid gland disorders are uncommon inchildren, many diseases may affect the parotid gland.Imaging modalities, such as US, CT and MRI help eval-uate and diagnose parotid gland lesions. Knowledge ofthe imaging findings is necessary for a specific diagnosisin an adequate clinical setting and as a guide to therapy.

References

1. Silvers AR, Som PM. Salivary glands. Radiol Clin North Am1998;36:941-966

2. Ying M, Ahuja A, Metreweli C. Diagnostic accuracy of sonograph-ic criteria for evaluation of cervical lymphadenopathy. JUltrasound Med 1998;17:437-445

3. Ying M, Ahuja A. Sonography of neck lymph nodes. Part I: normallymph nodes. Clin Radiol 2003;58:351-358

4. Som PM, Brandwein MS. Salivary glands: anatomy and pathology. InSom PM, Curtin HD. Head and Neck Imaging. 4th ed. St. Louis:Mosby, 2003:2027-2106

5. Garcia CJ, Flores PA, Arce JD, Chuaqui B, Schwartz DS.Ultrasonography in the study of salivary gland lesions in children.Pediatr Radiol 1998;28:418-425

6. Chitre VV, Premchandra DJ. Recurrent parotitis. Arch Dis Child1997;77:359-363

7. Siegel MJ. Face and neck. In Siegel MJ. Pediatric sonography. 3rded. St. Louis: Lippincott Williams and Wilkins, 2002:25-129

8. Cimaz R, Casadei A, Rose C, Bartunkova J, Sediva A, Falcini F, etal. Primary Sjogren syndrome in the paediatric age: a multicentresurvey. Eur J Pediatr 2003;162:661-665

9. Shapiro NL, Bhattacharyya N. Clinical characteristics and survivalfor major salivary gland malignancies in children. OtolaryngolHead Neck Surg 2006;134:631-634

10. Koch BL, Myer CM 3rd. Presentation and diagnosis of unilateralmaxillary swelling in children. Am J Otolaryngol 1999;20:106-129

11. Lowe LH, Stokes LS, Johnson JE, Heller RM, Royal SA,Wushensky C, et al. Swelling at the angle of the mandible: imagingof the pediatric parotid gland and periparotid region. Radiographics2001;21:1211-1227

12. Dunn P, Kuo TT, Shih LY, Lin TL, Wang PN, Kuo MC, et al.Primary salivary gland lymphoma: a clinicopathologic study of 23cases in Taiwan. Acta Haematol 2004;112:203-208

13. Xu Y, Wiernik PH. Systemic lupus erythematosus and B-cellhematologic neoplasm. Lupus 2001;10:841-850

14. Millman B, Pellitteri PK. Thyroid carcinoma in children and ado-lescents. Arch Otolaryngol Head Neck Surg 1995;121:1261-1264

15. Donnelly LF, Adams DM, Bisset GS 3rd. Vascular malformationsand hemangiomas: a practical approach in a multidisciplinary clin-ic. AJR Am J Roentgenol 2000;174:597-608

16. Toh H, Kodama J, Fukuda J, Rittman B, Mackenzie I. Incidenceand histology of human accessory parotid glands. Anat Rec1993;236:586-590

17. Currarino G, Votteler TP. Lesions of the accessory parotid gland inchildren. Pediatr Radiol 2006;36:1-7

18. Ahuja A, Ying M, Mok JS, Anil CM. Gray scale and powerDoppler sonography in cases of Kimura disease. AJNR Am JNeuroradiol 2001;22:513-517

19. Takahashi S, Ueda J, Furukawa T, Tsuda M, Nishimura M, OritaH, et al. Kimura disease: CT and MR findings. AJNR Am JNeuroradiol 1996;17:382-385

20. Samadi DS, Hockstein NG, Tom LW. Pediatric intraparotidCastleman’s disease. Ann Otol Rhinol Laryngol 2003;112:813-816

21. Iqbal Y, Al-Shaalan M, Al-Alola S, Afzal M, Al-Shehri S.Langerhans cell histiocytosis presenting as a painless bilateralswelling of the parotid glands. J Pediatr Hematol Oncol 2004;26:276-278

22. Maehara M, Ikeda K, Ohmura N, Sugimoto T, Harima K, Ino C, etal. Multislice computed tomography of pneumoparotid: a case re-port. Radiat Med 2005;23:147-150


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대한영상의학회지 2008;59:115-129

소아 이하선 질환의 다양한 영상 소견1

1성균관의대 삼성의료원 영상의학과

김유나·유소영·김지혜·어 홍

소아의 이하선 질환들은 상대적으로 드물기는 하나 다양한 양성 또는 악성 병변들이 이하선에 발생할 수 있어 이

에 대한 정확한 진단과 치료가 필수적이다. 이하선 병변이 의심될 때 초음파가 가장 우선으로 쓰이는 영상 기법이

며 임상 정보와 종합하여 정확한 진단을 내릴 수 있다. 그 외에도 컴퓨터단층촬영과 자기공명영상은 비전형적이거

나 크기가 크거나 또는 심엽에 위치한 병변들을 평가하는 데 좀 더 유용하다. 컴퓨터단층촬영은 염증성 병변, 타석

증, 농양, 이하선관 폐쇄에 대한 평가에서 우위를 가지며, 자기공명영상은 탁월한 연조직 해상도를 갖기 때문에 종

양의 위치나 범위를 평가할 때 더 나은 기법으로 여겨진다. 이에 우리는 여러 영상 기법들을 이용하여 소아의 다양

한 이하선 질환들의 영상 소견을 기술하려 한다.

Multimodality Imaging of Pediatric Parotid Gland Lesions 1

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