British Journal of Radiology (2005) 78, 75-85
© 2005 British Institute of Radiology
doi: 10.1259/bjr/15273006
Neck masses in children
J R A Turkington, FRCR,
A Paterson, FRCR,
L E Sweeney, FRCR and
G D Thornbury, FRCR
Department of Radiology, Royal Belfast Hospital for Sick Children, 180 Falls Road, Belfast BT12 6BE, UK
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Abstract
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Infants and children with neck masses frequently present to the radiologist for further evaluation. The role of the radiologist is to differentiate between conditions using imaging modalities such as ultrasound with colour Doppler, CT and MRI. Where appropriate, the radiologist will also stage lesions for management purposes and aid in guiding aspiration or biopsy. This paper presents a pictorial review of paediatric neck masses and their imaging features. Particular emphasis is applied to the anatomical site of the mass to aid in differential diagnosis. It must be emphasised that the radiological findings should always be interpreted in conjunction with the patient's age, the clinical history and the findings on physical examination.
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Introduction
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Neck masses are not uncommon in children. The most common aetiologies include congenital lesions and their complications, lymphadenopathy, vascular, inflammatory and malignant lesions. The role of the radiologist is to differentiate between these conditions using imaging modalities such as ultrasound (US) with colour Doppler, CT and MRI. US is useful to determine if a mass is cystic or solid and Doppler tells us if it is vascular. US should be considered as the first-line investigation because it is non invasive, does not require sedation and does not involve ionizing radiation [1]. CT and MRI can then be used to determine the extent of the lesion and whether local invasion is present. Both CT and MRI can provide multiplanar images, however MRI will more effectively demonstrate the soft tissue characteristics of a lesion.
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Anatomy
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The neck can be divided into the anterior and posterior triangles by the sternocleidomastoid (SCM) muscle (Figure 1
). To aid the radiologist, we have divided neck masses into cystic or solid lesions and listed them according to their anatomical location (anterior, posterior or either neck triangle). Lesions arising in the SCM muscle itself are discussed separately.
Anterior triangle masses
Thyroglossal cyst
Thyroglossal cysts usually manifest as an asymptomatic mass during childhood and lie within the anterior triangle [1]. They arise from a remnant of the thyroglossal duct. This extends from the foramen caecum at the base of the tongue to the pyramidal lobe of the thyroid gland, and usually involutes by the 8th week of intrauterine life. Remnants of a portion of the duct may lead to cyst formation or ectopic thyroid tissue. Thyroglossal cysts are midline or just off midline in position, and can be found at any level from the base of the tongue to the isthmus of the thyroid gland. Most (65%) are infrahyoid [5, 9]. On US they appear as a well-defined, thin-walled, anechoic mass with through enhancement (Figure 2). A mass with mixed echogenicity suggests infection of the cyst [5].
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Figure 2. Thyroglossal cyst. (a) Ultrasound shows a midline hypoechoic, avascular mass (arrow). (b) Axial short tau inversion recovery MRI confirms a high signal, well defined cyst (arrow).
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Branchial cyst
The branchial apparatus, consisting of six branchial arches separated by five branchial clefts appears by the 15th day of intrauterine life. Incomplete obliteration of the branchial apparatus, predominately the cleft, is postulated to lead to branchial cleft anomalies such as cysts, sinuses or fistulae [1]. Cysts may occur along the course of the first or second branchial clefts, however the majority (75%) arise from remnants of the second branchial cleft [9]. They occur in children and adolescents as a mass situated anterior to the SCM muscle and near to the angle of the mandible. A thin-walled, anechoic fluid-filled cyst is seen on US [5] (Figure 3a). With CT, the centre of the mass will have an attenuation value similar to water and if the cyst is infected, a thickened, enhancing wall will be present [9] (Figure 3b).
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Figure 3. (a) Ultrasound of an uncomplicated branchial cyst. Note the absence of septations and the through enhancement. (b) Axial contrast enhanced CT showing a right sided low attenuation branchial cyst.
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Dermoid/teratoma
Developmental anomalies which involve pleuripotent embryonal stem cells result in dermoid cysts and teratomas [1, 7]. Most occur in children less than 3 years of age and are situated in the midline [7]. They are usually suprahyoid, in contrast to thyroglossal cysts. On CT an inhomogenous, multiloculated mass that contains calcification and low attenuation fat enables the diagnosis [1, 7] (Figure 4). MR will show the fat component as high signal on T1 weighted images.
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Figure 4. Axial T1 weighted MRI of a mixed signal, right sided teratoma (arrows). The low signal cystic components and the intermediate signal fat can be identified.
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The thyroid gland
Thyroid masses are uncommon in childhood. They are best evaluated with US and radioisotope imaging. Diffuse enlargement of the gland can occur in thyrotoxicosis and Hashimoto's thyroiditis. The latter shows enlargement with variable echogenicity. In thyrotoxicosis the gland is enlarged, but the echopattern is similar to that of normal thyroid tissue [8]. With a focal thyroid mass US can easily differentiate whether the mass is solid or cystic. Most cystic masses in the region of the thyroid are likely to be thyroglossal cysts. Solid masses all have a similar US appearance of an echogenic mass. An adenoma is characteristically echogenic with a surrounding hypoechoic halo, carcinomas tend to demonstrate heterogeneous echogenicity. The differential diagnosis of a solid mass would also include lymphoma. A focal thyroid mass should be further investigated with an isotope thyroid scan and a "cold" nodule ultimately requires fine needle aspiration (FNA) or biopsy for histological diagnosis (Figure 5).
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Figure 5. (a) Isotope scan of thyroid demonstrating a photopenic area within the left lobe. (Reproduced with permission of Springer-Verlag [12]). (b) Axial contrast enhanced CT of the same patient shows a solid mass within left lobe of thyroid (arrows). Lymphoma was proven by biopsy.
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Salivary gland masses
Most salivary gland calculi occur in the submandibular gland in adolescents. The calculi may be identified on occlusal radiographs or with US. A sialogram will demonstrate a filling defect of a ductal stone and may also show glandular sialectasis due to ductal obstruction. Sialadenitis or inflammation of the salivary gland tends to affect the parotid gland in debilitated patients. The cause is usually due to oral cavity or dental sepsis with Staphylococcus aureus the most common pathogen [3]. It can also occur due to the mumps virus. US will demonstrate gland enlargement with abscess formation.
Recurrent parotiditis is rare but may result in unilateral, periodic, parotid swelling. The aetiology is unknown and non-obstructive sialectasis occurs. US shows hypoechoic intraglandular ductal dilatation, which can also be demonstrated with a sialogram or MRI [3] (Figure 6).
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Figure 6. (a) Parotid ultrasound demonstrating multiple hypoechoic areas representing dilated ducts (reproduced with permission of Springer-Verlag [12]). (b) Sialogram of same patient confirming intraglandular ductal beading of sialectasis of the left parotid gland.
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Posterior triangle masses
Lymphatic malformations
Congenital vascular and lymphatic malformations of the head and neck can be classified into two groups: vascular and lymphatic malformations and infantile haemangiomas [2]. The latter will be discussed later in this review. Vascular and lymphatic malformations grow in proportion to the child and almost never spontaneously involute. This group includes venous malformations (cavernous haemangiomas), capillary malformations (Port-wine stain) and lymphatic malformations (lymphangiomas and cystic hygromas). The previous terminology is listed in the brackets.
Lymphatic malformations (cystic hygromas) are congenital malformations resulting from blockage of lymphatic channels [6]. They usually present at birth as a painless swelling, and most lesions (90%) appear before the age of 2 years [2, 5, 6]. They are situated posterior to the SCM muscle in the posterior triangle. They tend to insinuate themselves around normal structures and can extend caudad into the superior mediastinum. Most are slow growing; however, sudden enlargement can occur following infection of or haemorrhage into the lesion, and may result in airway compression [2, 5, 6]. On US an anechoic or mixed echogenicity mass with septae of variable thickness will be identified [2, 4, 6]. Haemorrhage can lead to increased echogenicity or fluid–fluid levels being identified [2, 9]. The margins of the mass and the presence of mediastinal extension are better delineated with CT or MRI. CT will show a septated, low density, poorly circumscribed mass. Haemorrhage or infection causes an increase in attenuation. MRI will demonstrate a septated, cystic mass usually of high signal on T2 and low signal on T1 weighted images (Figure 7). Any high signal on T1 weighted images may reflect haemorrhage or a high lipid content. The insinuation around normal structures is well demonstrated on MRI and this can make complete surgical removal of the lesion difficult [6].
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Figure 7. (a) Ultrasound of a hypoechoic septated cystic hygroma. (b) Axial T2 weighted MRI of a well defined high signal right sided cystic hygroma (arrows). Note the insinuation around normal structures.
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Lipoma
This benign tumour of fat most commonly occurs in the posterior triangle of the neck. They are rare in children and appear as a solid, homogeneous mass of similar echogenicity to that of the subcutaneous fat [8]. On CT they will have low attenuation values of between –65 and –125 Hounsfield units indicating fat [1]. They often displace or compress adjacent structures; they are rarely infiltrative.
Lesions of the sternocleidomastoid muscle
Fibromatosis coli
This rare, benign condition presents in the neonatal period as a mass in the SCM muscle. Microscopically muscle is replaced by dense fibrous tissue [4]. A history of birth trauma and resulting torticollis is common. The clinical course is that of spontaneous resolution over a period of 4–8 months, with no treatment or with stretching exercises [4, 9]. US shows a uniformly isoechoic or hypoechoic mass within the muscle [4] (Figure 8). The mass can be seen to move with the muscle on real time ultrasound.
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Figure 8. Ultrasound of isoechoic mass (arrows) consistent with fibromatosis coli within the sternocleidomastoid muscle.
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Lesions presenting in either triangle of the neck
Infantile haemangioma
In contrast to congenital vascular and lymphatic malformations, infantile haemangiomas grow faster than the child and then spontaneously involute. Infantile haemangiomas of the head and neck usually occur in children less than 6 months of age, and this term includes the previously classified capillary haemangiomas, strawberry haemangiomas and capillary-cavernous haemangiomas [2]. Infantile haemangiomas usually grow rapidly until 9–10 months of age and then spontaneous regression occurs, which can take up to 10 years. Plain radiographs may show a soft tissue mass with areas of calcification representing phleboliths [9] (Figure 9). US demonstrates a mild to moderately echogenic mass, with echogenic septations that are vascular on colour Doppler interrogation. MRI is better at showing the relationship of the mass to the surrounding normal structures. The well-defined mass will be of high signal on T2 weighted images and contain flow voids, representing feeding and draining vessels [9] (Figure 9). An involuting haemangioma is less vascular and contains fibrofatty tissue and this is best demonstrated with MRI [2].
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Figure 9. (a) Lateral soft tissue neck radiograph of a haemangioma containing phleboliths (arrows). (b) Ultrasound demonstrating a soft tissue density mass with hypoechoic branching vascular channels. These were vascular on colour Doppler. (c) Axial T1 weighted MRI of a left sided, high signal haemangioma with vascular flow voids.
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Lymphadenitis
Cervical lymphadenitis usually results from a site of infection in the head and neck, such as the tonsils, pharynx or teeth [1]. US identifies numerous, discrete, enlarged, tender, oval masses of reduced echogenicity (Figure 10). Increased, branching vascularity is demonstrated with colour Doppler interrogation [8]. A necrotic lymph node will have a cystic hypoechoic centre [8].
Abscesses
Abscesses can occur in either triangle of the neck and also within the retropharyngeal space. On US a thick-walled, partially or fully fluid-filled mass will be present (Figure 11). Gas forming organisms cause small pockets of hyperechoic air within the collection. Enlarged, hypoechoic lymph nodes may be identified surrounding the abscess. Retropharyngeal abscesses commonly result from tonsillar infection and pre-vertebral soft tissue thickening can be identified on plain radiographs [9] (Figure 11).
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Figure 11. (a) Ultrasound of a mixed echogenic, thick walled, ill defined mass with central necrosis consistent with an abscess. (b) Radiograph showing extensive pre-vertebral soft tissue swelling of a retropharyngeal abscess (reproduced with permission of Springer-Verlag [12]).
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Rhabdomyosarcoma
This is the most common childhood soft tissue sarcoma and 40% occur in the head and neck [1, 11]. Embryonal rhabdomyosarcoma is the most common form, accounting for 60% of cases and occurring in the orbit, nasopharynx, middle ear, nasal cavity and paranasal sinuses [11]. Contrast enhanced CT and MRI are the best imaging modalities for diagnosis and staging. CT is valuable in demonstrating associated bony destruction. An enhancing aggressive soft tissue mass that may have foci of necrosis within it, is commonly demonstrated (Figure 12).
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Figure 12. Axial contrast enhanced CT of an inhomogeneous, enhancing, left sided, soft tissue mass within the anterior triangle (arrows). Histological diagnosis was rhabdomyosarcoma.
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Neuroblastoma
Most neuroblastomas arise in the adrenal glands, however they may originate anywhere along the sympathetic chain [9]. Most present before the age of 5 years [10] and those arising in the neck (5%) have a better prognosis than those tumours of adrenal origin [1]. Neuroblastoma can present as an asymptomatic mass, or along with local compressive symptoms, such as dysphagia, hoarseness, airway obstruction, Horner's syndrome or cranial nerve palsies. Imaging findings depend on the histology of the tumour and vary from a homogeneous well defined mass to a heterogeneous one with necrosis and haemorrhage. Calcification can be present, but is less common than in abdominal neuroblastomas [10]. US typically shows an echogenic mass. An unenhanced CT can demonstrate any calcification [1]. Following intravenous contrast medium, the mass of soft tissue density will enhance heterogeneously (Figure 13). MRI shows a tumour of high signal on T2 weighted sequences and enhancement is seen following the administration of intravenous gadolinium [10].
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Figure 13. Axial contrast enhanced CT demonstrating an irregular, enhancing right sided, biopsy proven neuroblastoma.
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Lymphoma
Lymphoma accounts for more than 55% of head and neck tumours in children [1]. Upper neck nodes are usually involved. If lower cervical nodes are involved, mediastinal nodes are also usually found. On US or CT large lymphomatous masses are identified and the involved lymph nodes are no longer discrete [1] (Figure 14). Central areas of necrosis within the nodal masses may also be seen.
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Figure 14. Axial contrast enhanced CT demonstrating multiple left sided lymph nodes and a right sided lymphomatous mass (arrows). Biopsy revealed Hodgkins lymphoma.
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Conclusions
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Neck masses are common in children and are a frequent cause of attendance in the Emergency Department. They can be classified according to their anatomical position in the neck and their appearance. The details in Table 1 can be used as an "aide-memoir" for the radiological differential diagnosis of paediatric soft tissue neck masses. After clinical examination, US should be the first modality used for investigation as it is readily available and does not involve ionizing radiation, unlike CT, and does not require sedation as is often the case with MRI in infants. It is particularly useful in assessing thyroid masses, thyroglossal and branchial cysts and parotid lesions. For other causes of neck masses it should still be the first line of investigation, after which CT and MRI can be used to determine the extent of the mass and better define its tissue characteristics.
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Conference paper
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Turkington JRA, Sweeney LE, Thornbury G, Paterson A. Neck masses in infants and children: a pictorial review. In: Royal College of Radiologists Annual Scientific Meeting, 10th–12th September 2003, London.
Received for publication December 22, 2003.
Revision received June 15, 2004.
Accepted for publication August 13, 2004.
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Abstract
Introduction
