Imaging of Cystic or Cyst-like Neck Masses

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REVIEW

Imaging of cystic or cyst-like neck masses

K.T. Wong, Y.Y.P. Lee, A.D. King, A.T. Ahuja*

Department of Diagnostic Radiology & Organ Imaging, Prince of Wales Hospital,

Chinese University of Hong Kong, Hong Kong

Received 18 October 2007; received in revised form 10 December 2007; accepted 14 December 2007

Cystic or cyst-like neck masses form a unique category within head and neck radiology with unique differential diag-noses. The precise anatomical location and imaging appearances are important for accurate diagnosis and formulatingthe differential diagnoses of cystic lesions in the neck. In vast majority of cases ultrasound, sometimes supplementedby fine-needle aspiration cytology (FNAC), is adequate for pre-treatment assessment. For large, deep-seated lesionsassessment using magnetic resonance imaging (MRI) or computed tomography (CT) often provides useful supplemen-tary information. Radiologists should be aware of imaging findings of common cystic neck masses to help in theirappropriate management. 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Introduction

A palpable neck mass is a commonly encounteredclinical problem. Meticulous clinical history andphysical examination may suggest the clinicaldiagnosis. Imaging is increasingly performed toconfirm the clinical diagnosis and assess theanatomical extent of involvement before anyform of treatment. Apart from its location, thedistinction between solid and cystic or cyst-likeneck masses helps in the definitive diagnosis or tonarrow the differential diagnoses.1 Cystic massesof the neck include a wide range of congenitaland acquired lesions. The vast majority of cysticlesions in infants and children are congenital or de-velopmental in origin, whereas inflammatory andneoplastic diseases constitute the majority of

cystic or cyst-like neck masses in adults. Althoughthere are overlapping features, differentiationbetween the lesions can usually be made based

on specific imaging findings and relevant clinicalinformation.

High-resolution ultrasound is an ideal initialimaging investigation for neck tumours.2 It is read-ily available, relatively inexpensive, and does not

involve ionizing radiation. Modern ultrasound ma-chines equipped with high-resolution transducersprovide excellent spatial and contrast resolution.Development of three-dimensional (3D) technol-ogy, extended field-of-view or panoramic imaging,and colour and power Doppler applications haveled to great improvements in diagnostic utilityand accuracy of ultrasound.3 Ultrasound also hasthe unique advantage over other imaging tech-niques in providing reliable, real-time guidancefor fine-needle aspiration cytology (FNAC) or corebiopsy.

Cross-sectional imaging techniques, such asmagnetic resonance imaging (MRI) and computedtomography (CT), serve a supplementary role inwork-up of cystic neck masses. The multiplanarcapability of MRI and multidetector CT allowsprecise preoperative anatomical localization,particularly for more deep-seated and locallyextensive lesions and T2-weighted MRI particu-larly helps to distinguish cystic from solidcomponents.

* Guarantor and correspondent: A.T. Ahuja, Department of Di-agnostic Radiology & Organ Imaging, Chinese University of HongKong, Prince of Wales Hospital, 30-32 Ngan Shing Street, ShatinN.T., Hong Kong. Tel.: 852 2632 1180; fax: 852 2648 7269.

E-mail address: [email protected] (A.T. Ahuja).

0009-9260/$ - see front matter 2007 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.crad.2007.12.007

Clinical Radiology (2008) 63, 613e622
mailto:[email protected]:[email protected]


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Site-specific differential diagnoses

The differential diagnoses of a cystic neck massdepend on the patients age and anatomicallocation of the lesion. Site-specific differentialdiagnoses of common cystic neck masses are

summarized in Table 1.

Submental region

Epidermoid/dermoid cyst

A dermoid cyst is the most common of theteratomatous lesions in the head and neck region,approximately 7% occur of all dermoids occurringin this region.4 Histologically it contains two germcell layers and skin appendages (e.g., hair follicles

and sebaceous glands). An epidermoid cyst is lesscommon in the neck than a dermoid cyst and iscomprised solely of ectoderm.

Dermoid/epidermoid cysts are frequently mid-line in location, typically arising either in the floorof mouth deep to the mylohyoid muscles or in thesuprasternal notch. They may also occur in the

orbit, nasal, and oral cavities. The sebaceoussecretions result in slow enlargement of theselesions.

On ultrasound, the cyst is usually well-definedand anechoic with posterior acoustic enhancementin a midline position of the neck.2 Due to the pres-

ence of cellular material within the cyst, it mayexhibit a pseudosolid appearance on ultrasoundwith uniform homogeneous internal echoes. Der-moid cysts may have mixed internal echoes becauseof its fat content and may show the presence ofosseo-dental structures within, seen as echogenicfoci with dense posterior acoustic shadowing.

On CT or MRI, globules of fat floating within thelesion may produce a characteristic sack ofmarbles appearance, and fat and/or fluid levelsmay be present (Fig. 1). Both CT and MRI clearlydefine their anatomical location, extent, andinternal appearance.5

Ranula

A ranula is a mucous retention cyst resulting fromobstruction of the sublingual gland or its duct, orrarely the minor salivary glands in the sublingualspace.6,7 There are two forms: (1) simple ranula,which is the most common form and invariably in-volves the sublingual gland. It is a true cyst with anepithelial lining. Anatomically it is confined withinthe floor of mouth deep to the level of mylohyoidmuscle. (2) Diving ranula, which forms from en-

largement of a simple ranula with subsequent

Table 1 Common cystic neck masses based on anatomicallocation

Submental region Dermoid/epidermoidRanula

Midline/thyroid region Thyroglossal duct cystAcute suppurative thyroiditisColloid and haemorrhagic

thyroid cystic noduleThymic cyst

Submandibular region Second branchial cleft cystAbscessDiving ranulaCystic metastatic lymph node

Parotid region Extraglandular mass- First branchial cleft cyst

Intraglandular mass- Warthins tumour- Acquired cysts of parotid gland- Rare vascular lesions

(pseudoaneurysm,arteriovenous fistula/malformation, venousvascular malformation)

Along cervical chain Cystic metastatic lymph nodeVenous vascular malformationSecond branchial cleft cystAbscessDistended internal jugular vein

Posterior triangle LymphangiomaVenous vascular malformationCystic metastatic lymph nodeTuberculous lymphadenitis

Figure 1 Axial, fat-suppressed, T2-weighted MRI im-age shows the characteristic appearances of a midlinedermoid cyst in the floor of mouth with a sack ofmarbles appearance (arrow) due to presence of fatglobules (arrowheads) within the dermoid cyst.

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rupture that extends posteriorly around the poste-rior free margin of mylohyoid muscle, through itsfibres or defect of the mylohyoid muscle (i.e.,boutonniere anomaly, which is present in 77% ofnormal individuals undergoing CT8) into the sub-mandibular space. Therefore, anatomically it

extends superficially to the level of mylohyoidmuscle. It is a pseudocyst and is not lined byepithelium.

On ultrasound, a ranula appears as a unilocular,well-defined, cystic lesion in the submental regionrelated to the sublingual gland (Fig. 2). It may con-tain fine internal echoes, usually due to presenceof debris from previous episodes of inflammation.For a diving ranula, the bulk of the cystic collec-tion is in the submandibular region, but a smallbeak may be seen within the sublingual space.2

On CT, a simple ranula usually appears as anovoid-shaped cyst with an homogeneous centralattenuation region of 10

e20 HU, which lies lateral

to the genioglossal muscles and deep to the mylo-hyoid muscle. A diving ranula often infiltratesadjacent tissue planes, extending inferiorly anddorsally to the submandibular space. On MRI, a ran-ula usually shows low signal intensity on the T1-weighted sequence and high signal on T2-weightedsequence. Occasionally when the protein contentof the cystic fluid is high, the lesion will appearhyperintense on the T1-weighted sequence.9

Midline/thyroid region

Thyroglossal duct cyst

In the third to fourth week of fetal developmentthe paired thyroid primordia descend into the neck

along the thyroglossal duct that runs from theforamen caecum at the base of the tongue tothe lower anterior neck, passing the hyoid bone.The duct normally involutes by the eighth week.10

Persistence of the duct or a portion of the duct canlead to congenital anomalies, such as ectopicthyroid tissue or thyroglossal duct cysts (TDC).The majority of TDCs are infrahyoid (25e65%),15e50% occur at the level of the hyoid, and20e25% are suprahyoid in location.11 Patientsusually present with a painless midline mass andthere is often a history of previous incision and

drainage at the site.

12

About 50% present beforethe age of 10 years, the second group of patientspresenting in young adulthood.

On ultrasound, TDCs may appear (1) franklycystic with homogeneous anechoic internalappearance and posterior acoustic enhancement;(2) hypoechoic echopattern with internal debris;(3) heterogeneous echopattern, probably due torepeated infections or haemorrhage; or (4)uniformly echogenic pseudosolid appearance(Fig. 3) due to the proteinaceous content of thecyst secreted by the epithelial lining.13,14

Figure 2 Transverse grey-scale ultrasound imageshows a well-defined, lobulate cystic lesion (arrows) inthe left submental region deep to the mylohyoid muscle(arrowheads) and closely related to the left sublingualgland (not shown) compatible with a ranula.

Figure 3 Longitudinal grey-scale ultrasound of ante-rior neck in the midline shows an infrahyoid thyroglossalduct cyst (arrow) with a pseudosolid appearance. Notethe posterior enhancement. Arrowhead marks the hyoidbone.

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On MRI, TDCs are invariably hyperintense onT2-weighted sequences. The signal intensity on T1-weighted images is highly variable due to differ-ence in cystic content, with T1-hyperintensityseen in lesions with high proteinaceous cysticcontent.15

On preoperative imaging work-up of a patientwith thyroglossal duct cyst, the following aspectsneed to be considered16: (1) thyroid carcinoma candevelop in a TDC, with an incidence of 1% in adults:95% papillary adenocarcinoma, 5% squamous cellcarcinoma.17,18 Therefore, any solid componentwithin a cyst requires FNAC if the cyst is not goingto be excised. (2) Normal thyroid tissue has tobe identified by ultrasound in the anterior neckbefore surgery to prevent postoperative hypothy-roidism. (3) The relationship of the TDC with thehyoid bone must be determined as it helps thesurgeon to completely excise the lesion so reducingthe chance of a postoperative recurrence.

Acute suppurative thyroiditis

Acute suppurative thyroiditis is more common inchildren. It has a left-sided predominance and isfrequently associated with a fourth branchial cleftanomaly. The child typically presents acutely withpain, thyroid swelling, fever, and odynophagia.There is usually a history of previous similarepisodes or evidence of multiple incision and

drainage. The infection usually begins in theperithyroidal soft tissues. The thyroid gland isrelatively resistant to infection due to its inher-ently high iodine content and the presence ofa thick fibrous capsule, so it tends to be involvedonly in the later stage of infection.2

On ultrasound, both intra- and extra-thyroidabscesses are seen as ill-defined, hypoechoic,heterogeneous areas with internal debris. Occa-sionally small echogenic foci with reverberationartefacts due to the presence of gas bubbles aredemonstrated. The fascial planes between thethyroid gland and perithyroidal soft tissue areobliterated.2 Adjacent reactive lymph nodes arefrequently present. Apart from diagnosis, ultra-sound enables real-time guidance for needle aspi-ration, if necessary, and to monitor the responseto antibiotic treatment.

In complicated cases or if there is suboptimalresponse to medical treatment, CT is useful formore exact anatomical delineation of the suppu-rative process before surgical drainage. After theinfection has settled, a barium study is indicatedto identify any associated piriform fossa sinus.19

CT and MRI have also been used to demonstrate

the presence of the abscess and the fistula tractfrom the piriform fossa.20,21

Colloid and haemorrhagic thyroid cysticnodule

True epithelial thyroid cysts are rare.22 Most cysticthyroid lesions are due to haemorrhage or degen-eration within a hyperplastic nodule, which isusually part of a multinodular goitre.

On ultrasound, these appear as well-defined,heterogeneous nodules with a cystic componentand internal septa. The comet tail sign, suggestingthe presence of colloid within, is occasionallyseen.23 The presence of multiple cystic nodules isdiagnostic of multinodular thyroid. It should benoted that about 20e30% of papillary carcinomashave a cystic component that may mimic benign

cystic thyroid nodules. The presence of character-istic punctuate calcifications and chaotic intranod-ular vascularity on power Doppler examinationraises the suspicion of a malignant lesion, whichwould necessitate further assessment using FNAC.

Thymic cyst

The thymus gland forms when the paired thymicprimordia complete their inferior migration alongthe thymopharyngeal ducts and fuse. Obliterationof the lumen of the thymopharyngeal tract occurs

during the seventh and eighth week of gestation.10

Persistence or sequestered remnants of the thymo-pharyngeal duct lead to the development ofthymic cyst. Thymic cyst is uncommon, with mostlesions detected as an incidental imaging finding.It may be present anywhere from the angle ofthe mandible to the superior mediastinumadjacent to the carotid sheath. A connectionwith mediastinal thymic tissue may be present.24

On ultrasound it appears as a well-defined,anechoic cystic lesion below the level of thethyroid gland and related to the carotid sheath.

On CT, the cyst wall is thin and uniformly smooth,and the cyst content is of mucoid attenuation(10e25 HU). On MRI, the cystic content usuallyhas low to intermediate T1-weighted and highT2-weighted signal intensity.4

Submandibular region

Abscess

An abscess in the submandibular area usuallyoriginates from suppurative adenopthy, salivary



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gland infection, dental abscess, or mandibularosteomyelitis. On ultrasound, an abscess appearsas an ill-defined, irregular collection with thickwalls and internal debris. It may be unilocular ormultilocular. The adjacent soft tissues are oedem-atous with loss of fascial planes. Enlarged reactive

regional lymph nodes are commonly seen. The rimof the abscess may demonstrate hypervascularityon power Doppler imaging.2

On CT, an abscess usually appears as a single ormulti-loculated low density area with rim en-hancement (Fig. 4). Internal gas collections maybe present. The adjacent subcutaneous and fascialfat planes are often obliterated. On MRI, anabscess typically has low T1-weighted and highT2-weighted signal intensities. Rim or thick periph-eral enhancement is commonly seen in a matureneck abscess.7

Ultrasound helps to confirm the clinical diagno-sis of abscess, delineate its anatomical locationbefore surgery or aspiration, identify complica-tions such as venous thrombosis or carotidinvolvement, and provide real-time imaging guid-ance for aspiration.

Second branchial cleft cyst (BCC)

Of all the branchial cleft anomalies, 95% arise fromthe remnants of the second branchial apparatus,

the most common form is second BCC.6 This typi-cally presents as a cystic mass at the angle of themandible and is more common in children andyoung adults. The site of second BCC is embryolog-ically defined, typically located superficial to thecommon carotid artery and internal jugular vein,

posterior to the submandibular gland and alongthe medial and anterior margin of the sternoclei-domastoid muscle.2

On ultrasound, most uninfected second BCCsdemonstrate the typical appearances of a cyst inthat they are well-defined and anechoic with nointernal debris and show posterior acousticenhancement (Fig. 5); however, some cysts mayexhibit a pseudosolid appearance with uniforminternal echoes. This is due to proteinaceous con-tent, such as mucus, debris, lymphocytes, epithe-lial cells, and cholesterol crystals, within thecyst.25 BCCs complicated by previous infection/inflammation are usually ill-defined, heteroge-neous, and thick-walled, containing internal debrisand septa. Such cysts mimic metastatic nodes frompapillary carcinoma of thyroid or squamous cellcarcinoma.26 In these cases FNAC of any solidmural component is recommended to excludea metastatic lymph node.

CT or MRI may be indicated if a sinus or fistula issuspected. If a beak is identified on ultrasoundpointing medially, then it is prudent to obtainfurther imaging in order to exclude a sinus orfistula. On CT, second BCC appears as a homo-

geneous mass with low attenuation and a thin,

Figure 4 Contrast-enhanced CT image shows an ill-defined fluid collection with peripheral enhancement(arrow) posterior to the left submandibular gland(arrowhead) compatible with an abscess. Note theextension of the suppurative process to adjacentretropharyngeal space (open arrow) and paralaryngealarea (curved arrow).

Figure 5 Transverse grey-scale ultrasound image ofright upper neck shows a well-circumscribed anechoiccystic lesion (arrow) posterior to the submandibulargland (arrowhead) and superficial to internal carotidartery (open arrow). The anatomical location andappearances are compatible with a second BCC.



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well-defined wall in the typical location, i.e.,posterior to submandibular gland, anterior tomajor vessels and medial to the anterior margin ofsternocleidomastoid muscle. Conversely, infectedcysts can be hyperattenuated with an ill-defined,irregular rim, mimicking a metastatic node.1 On

MRI, the T2-weighted signal intensity is invariablyhigh due to presence of intracystic fluid. The pro-teinaceous content of the cyst may some timescause it to appear hyperintense rather than isoin-tense or hypointense on T1-weighted series.27

Cystic metastatic lymph node and divingranula

Cystic metastatic lymph node and diving ranula arealso found in this region and are referred toelsewhere in the text.

Parotid region

Extra-glandular lesions

First BCC. A first BCC arises from abnormal em-bryogenesis of the first branchial apparatus and ac-counts for 8% of all branchial cleft abnormalities.1

It may be associated with changes in the temporalbone in the form of a tract through the externalauditory canal and temporal bone. Anatomically

first BCC occurs in and around the parotid gland,external auditory canal and the angle of the man-dible. The typical history is a middle-age femalewith history of recurrent parotid abscesses.

On ultrasound, a first BCC may appear as trulycystic with anechoic content, homogeneous hyper-echoic with a pseudosolid appearance or hetero-geneous hypoechoic with internal debris ininfected cysts.2 The key to the correct diagnosisis the close anatomical location with the parotidgland.

On CT, a first BCC appears as well-defined,thin-walled lesion of mucoid attenuation (10e25

HU), whereas on MRI, it is usually of low tointermediate T1-weighted and high T2-weightedsignal intensity.4

Intra-glandular lesions

Warthins tumour. Warthins tumour is a benignsalivary gland tumour that accounts for 6e10% ofparotid tumours.9 About 15% of patients have bilat-eral involvement.

On ultrasound, Warthins tumour is typicallya well-circumscribed, hypoechoic mass in the

parotid tail with internal heterogeneity (solid andcystic components) and posterior acoustic enhan-cement.28 The classical appearances of a well-defined, multiseptate, cystic internal architecturehas a high specificity for the diagnosis of Warthinstumour.29 Power Doppler ultrasound may show

vessels in a hilar distribution with branches in thesepta of the structure. On MRI, Warthins tumourusually appears as well-circumscribed, hetero-geneous lesion with mixed cystic and enhancingsolid components.9

Acquired cysts of parotid gland. Congenitalepithelial cysts of the parotid gland are rare. Theacquired cystic lesions in parotid gland consistmainly of (1) ductal cysts/sialocysts that developas a result of ductal obstruction, which may becaused by a post-inflammatory stricture, calculus,trauma or post-surgery. (2) Lymphoepithelial cysts,which are more commonly seen in children andpatients with human immunodeficiency virus (HIV)infection.

Rare vascular lesions.30 Vascular lesions withinthe parotid gland are rare. Three vascular lesionsmay occasionally be encountered and present clin-ically as a parotid mass. These include: (1) pseu-doaneurysm (from branches of external carotidartery), which on ultrasound appears as a well-circumscribed, hypoechoic mass with an internalcystic component. On power Doppler imaging,the cystic component demonstrates chaotic arte-rial flow with adjacent supplying artery. On MRI,

pseudoaneurysm shows isointense T1 and hyperin-tense T2 signal intensity with avid homogeneousenhancement after intravenous gadolinium. An an-giogram helps to confirm the diagnosis, identifythe artery of origin, and plan surgical or endovas-cular treatment; (2) arteriovenous fistula/malfor-mation, which on ultrasound appears as an areaof multiple serpinginous anechoic structureswith blood flow on grey-scale and power Dopplerultrasound. Engorged draining veins are seen in itsvicinity. MRI helps to depict the lesion with nu-merous serpinginous signal voids. The supplyingarteries and engorged draining veins are welldemonstrated using MRA and digital subtractionangiography; (3) venous vascular malformation,which on ultrasound it appears as a well-definedheterogeneous lesion with multiple anechoic sinu-soidal spaces with slow flow on grey-scale imagingand presence of phleboliths. The lesion is typi-cally hypovascular on power Doppler examina-tion. On MRI, venous vascular malformation ofparotid is hypo/isointense on T1-weighted se-quence, markedly hyperintense on T2-weightedsequence with avid enhancement after intrave-nous gadolinium.



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Cystic mass along cervical chain

Cystic metastatic lymph node

Metastatic cervical lymph nodes from squamouscell carcinoma of the head and neck and papillary

carcinoma of thyroid gland are the most commontypes of nodal metastases with intranodal cysticnecrosis.31,32 On ultrasound cystic necrosis maymanifest itself as a truly cystic area or as a central,ill-defined area of relative hypoechogenicity ac-companied by eccentric solid component withinan enlarged lymph node.33,34 The solid areas usu-ally demonstrate increased peripheral and chaoticvascularity on Doppler (Fig. 6).35,36 The presenceof characteristic punctuate calcifications withinthe solid component of the cystic node should alertthe radiologist towards a careful search for

primary papillary carcinoma in the thyroid gland.Occasionally cystic necrosis within a metastaticlymph node may be very florid, mimicking a con-genital cyst, such as a second BCC.26

On CT, cystic nodal necrosis appears as focalarea of low attenuation with or without a surround-ing rim of soft-tissue enhancement. On MRI, thepresence of a focal area of high signal intensity onT2-weighted images or low signal intensity on T1-weighted images with or without a surrounding rimof enhancement suggest the presence of nodalnecrosis.37 The sensitivity of MRI and CT is shown

to be better than that of high-resolutionultrasound.37

Venous vascular malformation

Approximately 15% of venous vascular malforma-

tions occur in the head and neck, the massetermuscle being the most common site. Althoughprimarily a vascular malformation with largecavernous spaces, there may also be lymphaticelements present. The role of imaging is to identifythe exact anatomical location and the extent ofthe lesion before therapy. The diagnosis is readilymade by ultrasound, particularly when the pres-ence of phlebolith is demonstrated. MRI is the bestimaging technique to depict the exact anatomicallocation and extent, especially for large and deep-seated lesions.38

The ultrasound appearances are fairly charac-teristic and show a lesion with a hypoechoic,heterogeneous echopattern with multiple sinu-soidal spaces. Phleboliths are seen in 22% ofcases (Fig. 7),38,39 although with the newer high-resolution transducers they are more commonlydetected in head and neck venous vascular malfor-mation, especially in adults. Although powerDoppler may depict the slow flowing nature ofvenous vascular malformation, the flow phenome-non is usually better demonstrated on real-timegrey-scale ultrasound.

On MRI, venous vascular malformation shows

a characteristic high signal on T2-weighted fat-saturated sequences ensuring its conspicuity.38

Although MRI may not be as sensitive as ultrasoundin the identification of phleboliths, it is excellent(better than CT and ultrasound) at depicting the

Figure 6 Transverse grey-scale ultrasound image ofright upper cervical level shows an enlarged lymphnode (arrow) with cystic intranodal necrosis (arrow-head). At histology a metastatic squamous cellcarcinoma was diagnosed. Note the presence of chaoticperipheral vascularity (open arrows) within the solidcomponent of the metastatic node on power Dopplerultrasound.

Figure 7 Transverse grey-scale ultrasound at rightlower cervical level shows a heterogeneous lesion(arrows) with multiple anechoic sinusoidal spaces,septa, and phlebolith (arrowhead) compatible witha venous vascular malformation.



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full extent of large venous vascular malformations,which may be trans-spatial.

Second BCC and abscesses

Second BCC and abscesses are discussed above.

Distended internal jugular vein

Phlebectasia is dilatation of an isolated vein, andthe internal jugular vein is the most commonlyaffected. It may present with cervical swellingthat expands with increased intrathoracic pres-sure.40 Ultrasound supplemented by Doppler ultra-sound examination accurately identifies thedilated internal jugular vein and venous bloodflow on the Valsalva manoeuvre.40,41

Posterior triangle

Lymphangioma

Lymphatic malformations are congenital abnor-malities that arise when developing lymphaticsfail to establish communication with developingveins.42,43 They can be divided into three types:(1) cystic hygroma, which has large lymphaticspaces; (2) cavernous lymphangioma, which hassmaller spaces and develops from buds that wouldhave formed terminal lymphatics; (3) capillary

lymphangioma, which contains the smallest cysticspaces.

The cystic hygroma is the most commonlyencountered type and typically presents in chil-dren, of which 50e60% present at birth or perina-tally, and 30% present by age of 2 years.4 Theyusually present clinically as painless compressibleneck mass, more commonly in the posterior trian-gle. Following haemorrhage they can enlarge rap-idly and become tense.4 Large lesions can involvemore than one anatomical space and so theprimary role of imaging is to demonstrate theanatomical extent before surgery or sclerotherapy.

On ultrasound, cystic hygroma appears as a com-pressible multiloculate cystic lesion with interven-ing thin septa. Vascularity may be seen within thesepta. Large lesions tend to be transpatial andfollow no obvious anatomical boundaries. If thereis a previous episode of haemorrhage or infection,they may contain internal low-level echoes debrisand show irregular walls.1,2,27

Although the diagnosis can easily be obtained byultrasound, MRI or CT is often required to demon-strate the extension to other compartments of theneck that it can involve. T2-weighted sequence

offers superb contrast resolution for delineation ofthe extent of cystic hygromas, which invariablyappear as high signal intensity masses with multi-ple internal septae (Fig. 8).27,42 In patients treatedby sclerotherapy with OK-432 (Pacibanil) injection,serial MRI helps to assess treatment response and

the necessity for repeated injection.44,45

Venous vascular malformation and cysticmetastatic lymph node

Venous vascular malformation and cystic meta-static lymph node are referred to above.

Tuberculous lymphadenitis

Tuberculous lymphadenitis has a predilection forthe posterior triangle of the neck. On imaging, it

may appear almost entirely cystic or necrotic andmimic a cystic metastatic lymph node. The pres-ence of nodal matting, surrounding soft-tissueoedema, avascularity, or displaced hilar vesselson power Doppler ultrasound examination areclues that may suggest a tuberculous rather than

Figure 8 Coronal, T2-weighted, MRI image showsa large cystic lesion (arrow) with internal septa (arrow-heads) in right lower posterior triangle compatiblewith a cystic hygroma/macrocystic lymphangioma.



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a metastatic cause.34,46,47 However, there isoverlap of appearance in these two entities andFNA for microbiological culture and cytology isusually required.

Summary

The precise anatomical location and imagingappearances are important for the accuratediagnosis and formulating the differential diagno-ses of cystic lesions in the neck. In the vastmajority of cases ultrasound, sometimes supple-mented by FNAC, is adequate for pre-treatmentassessment. For large deep-seated lesions assess-ment with MRI or CT provides useful supplemen-tary information. Radiologists should be aware ofthe imaging findings of common cystic neck masses

to help in their appropriate management.

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