2017 Sec 1 Green Book

Fig 18.

Axial T1-weighted (A), coronal fat-suppressed T2-weighted (B), and axial fat-suppressed postcontrast T1-weighted (B) MR images

of a child with a large lipoma. The axial image (A) shows a homogenous mass in the left periclavicular region with signal intensity similar to

subcutaneous fat. The postcontrast image (C) demonstrates no enhancement after contrast administration. The fat suppressed images (B, C)

confirm the diagnosis of lipoma by homogenous suppression of the lesion in comparison with the conventional T1-weighted image (A).

of the cervical region are more common.

The lesion often

presents in young childhood, before the age of 5 years, as

an asymptomatic mass or with symptoms due to compres-

sion of adjacent structures (eg, dysphagia, airway obstruction,

Horner’s syndrome). Primary cervical neuroblastic tumors have

a more favorable outcome compared to lesions of adrenal

origin.

1,5

Neuroblastomas, ganglioneuroblastomas, and gan-

glioneuromas are tumors of varying maturity derived from pri-

mordial neural crest cells destined for sympathetic differentia-

tion and may arise anywhere along the sympathetic ganglia.

Neuroblastomas are primarily composed of undifferentiated

neuroblasts, ganglioneuromas consist of mature ganglion cells

and other mature tissue, and ganglioneuroblastomas have both

immature and mature cell types. As a consequence, neurob-

lastomas and ganglioneuroblastomas are potential malignant

lesions and ganglioneuromas are considered benign.

Imag-

ing features consist of an echogenic posterior cervical mass on

US and a T2 hyperintense mass with contrast enhancement on

MR imaging. The overall aspect of the mass may vary from

homogeneous to heterogeneous with necrosis and hemorrhage

based on the degree of maturation and aggressiveness of the

lesion. Meta-iodobenzylguanidine (mIBG) scintigraphy shows

vigorous radiotracer uptake in neuroblastic tumors and aids in

differentiating these tumors from other posterior cervical mass

lesions.

Furthermore, catecholamines in the urine are in most

cases elevated.

Lymphadenitis

Enlarged cervical lymph nodes are the most common palpa-

ble neck masses in the pediatric population as 80–90% of the

children between 4 and 8 years have palpable cervical lymph

nodes.

The most frequent etiology in cervical lymphadenitis is a

viral infection of the upper respiratory tract. The bilateral sub-

mandibular and upper internal jugular lymph nodes are typi-

cally involved. In case of bacterial infection, unilateral lymph

node involvement is frequently noted.

6,60

US is the imaging

method of choice to identify reactive lymphadenopathy and

possible complications including suppurative inflammation or

abscess formation. Reactive lymph nodes are enlarged (

1 cm

short axis), ovoid, and rounded in shape and may be hyper-

vascular on Doppler US. The vascular hilum is preserved and

the vessels fan out from the hilum. Inflammatory lymph nodes

are enlarged and may appear as confluent lesions. Liquefac-

tion and suppuration causes the central part of the lymph node

to become hypoechoic on US or hypodens on CT (Fig 19).

Necrotic lesions may have areas of decreased vascularity.

6,61

Infected cystic anomalies of the head and neck region

(eg, thyroglossal duct cysts, branchial cleft cysts, and thymopha-

ryngeal duct cysts) can mimic suppurative lymphadenitis on US

and CT.

Nontuberculous mycobacteria (NTM) is an increasing rec-

ognized cause of infection in the pediatric population. The most

common causative organisms are

Mycobacterium avium

My-

cobacterium intracellulare.

Typically, this entity manifests as per-

sistent, and sometimes gradually enlarging, unilateral cervical

lymphadenitis in immunocompetent children. There is a prefer-

ence for submandibular, parotid, or preauricular lymph nodes.

Signs of acute inflammation, tenderness, fever, or other systemic

signs of infection are frequently lacking. The peak age of inci-

dence is between 2 and 4 years.

62,63

Because nontuberculous

mycobacterial lymphadenitis is unresponsive to conventional

antibiotics, as opposed to suppurative bacterial lymphadenitis,

early recognition of this specific type of adenitis leads to ap-

propriate therapy (surgical excision) early in the course of the

disease. The CT or MR imaging findings include asymmet-

ric enlarged cervical lymph nodes and extranodal extension

as contiguous necrotic ring-enhancing mass lesions involving

the subcutaneous fat and skin. Inflammatory stranding of the

subcutaneous fat is typically minimal or absent (unlike bacte-

rial abscesses).

Bacterial lymphadenitis and cat-scratch disease

in general cause painful enlarging lymph nodes. Tuberculosis

demonstrates bilateral lymphadenitis in the posterior cervical

triangle and is usually painless.

Abscesses are hypoechoic or anechoic lesions on US imag-

ing with a variable thick rim of solid tissue and they may show

septations. Gentle pressure applied with the US probe typically

causes swirling of the contents of the abscess.

CT as well as

MRI are useful in the evaluation in children suspected of having

a deep neck abscess (Fig 19). The ACR Appropriateness Crite-

ria prefer CT over MRI because of the short examination time

and lack of need for anesthesia. The use of intravenous contrast

administration is essential for detecting neck abscesses, in par-

ticular intramuscular abscesses and retropharyngeal abscesses.

The use of diffusion-weighted MRI sequences in the evaluation

of a suspected neck abscess is of great value because of the char-

acteristic demonstration of restricted diffusion of the content of

Dremmen et al: Imaging Lumps and Bumps of the Neck in Children

185