2017 Sec 1 Green Book

Fig 19.

Axial (A, B) and coronal (C) contrast-enhanced CT images in soft tissue window of a child with cervical lymphadenitis as a consequence

of a bacterial infection of the upper respiratory tract. Multiple enlarged reactive lymph nodes are demonstrated in the right upper cervical region

(A). Some of the involved lymph nodes appear as confluent lesions (A). Liquefaction and suppuration causes the central part of the lymph

node to become hypodens (B, C). Subsequent abscess formation is shown by extranodal extension (B, C). Note the unilateral lymph node

involvement as frequently occurs in case of bacterial infection.

the abscess due to reduced water mobility within the pus.

Ad-

ditional MRA and MRV imaging sequences may be of great

value to exclude associated vascular complications, eg, venous

thrombosis or development of Lemierre’s syndrome.

Lymphoma

Lymphoma is the most common malignancy arising from the

head and neck region in the pediatric population (55% of head

and neck tumors in children). In general, lymphomas account

for 10–15% of all childhood malignancies.

1,5

The lesion typi-

cally presents as a painless posterior neck mass or supraclavic-

ular mass, often in association with lymph node enlargement

in other cervical regions. The vast majority of cervical lymph

node enlargement in children is the result of viral or bacterial

upper respiratory tract infection. Persistent nodal enlargement

(for more than 6 weeks) requires further evaluation.

On US

(including color Doppler), features differentiating nodal malig-

nancies from benign reactive lymph nodes include increased

size (

3 cm in longest diameter), round shape, decrease in

internal echogenicity, loss of normal echogenic hilum, detec-

tion of peripheral subcapsular vessels, and focal areas of absent

perfusion.

1,5

Currently, disease staging of lymphoma is prefer-

ably performed with CT of the neck, chest, abdomen, and

pelvis. Lymph nodes demonstrating a short axis

2 cm are con-

sidered to be involved in the disease process. For intermediate-

sized lymph nodes (10-20 mm), radiotracer uptake on positron

emission tomography (PET) indicates involvement.

MR imag-

ing is typically used for evaluation of central nervous sys-

tem involvement. However, diffusion-weighted MR imaging

sequences may also play a role in differentiating involved from

noninvolved lymph nodes by calculating the mean apparent

diffusion coefficient (ADC) value. The ADC value of involved

lymph nodes is significantly lower compared to noninvolved

lymph nodes due to the high cellularity in lymphoma.

The

future role for PET MR imaging in the staging of this disease is

promising.

Hodgkin lymphoma is more common in adolescents. The

classical appearance of Hodgkin lymphoma is involvement of

contiguous lymph node groups. Coexistent mediastinal lymph

node involvement is common. The disease is often confined

to the neck and chest region (Fig 20). Staging of disease

is performed according to the Cotswold modification of the

Ann Arbor staging system.

5,64

The staging system differentiates

single from multiple lymph node group involvement and takes

into account if the lymph node groups are located on the same

side or on both sides of the diaphragm, bulk size, extranodal

sites of disease, and presence of clinical symptoms (B-symptoms

including night sweating, weight loss, and malaise).

Non-Hodgkin lymphoma is more common than Hodgkin

lymphoma in children younger than 10 years of age. Four

subtypes are differentiated in the World Health Organiza-

tion (WHO) classification: Burkitt lymphoma, diffuse large

B-cell lymphoma, anaplastic large cell lymphoma, and lym-

phoblastic lymphoma. Cervical non-Hodgkin lymphoma is of-

ten accompanied by disseminated disease. Furthermore, non-

Hodgkin lymphoma may involve extranodal lymphatic sites

(eg, Waldeyer ring) or other extranodal sites (eg, jaw) in the

cervical region. In the pediatric age group, cervical extranodal

disease in non-Hodgkin lymphoma is less common than in

other body parts.

In 2015, a new staging system for the pedi-

atric age group has been introduced based on identification of

new pathologic entities, improvements in cytogenetic, molec-

ular, and immunophenotypic characterizations of disease and

major advances in imaging applicable to childhood and ado-

lescent non-Hodgkin lymphoma. The revised International Pe-

diatric Non-Hodgkin Lymphoma Staging System (IPNHLSS)

maintains the general structure of the St. Jude staging system

and introduces some modifications and more explicit indica-

tions on peculiar sites of disease.

The staging system basically

assesses tumor load and differentiates limited disease form ex-

tensive disease.

Rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft tissue sarcoma in

children younger than 5 years of age. Forty percent of the rhab-

domyosarcomas are located in the head and neck region.

1,5,66

The lesion generally manifests in the first decade of life and

demonstrates a slight male predominance. There are three prin-

cipal histologic subtypes acknowledged, the embryonal, alveo-

lar, and pleomorphic type. The embryonal subtype has in gen-

eral a better prognosis, whereas alveolar rhabdomyosarcomas

belong to the most aggressive types. Tumors of the embryonal

subtype account for 60% of the rhabdomyosarcomas, and there-

fore site of origin of the tumor in the head and neck region

is associated with favorable outcome. Head and neck rhab-

domyosarcomas are categorized into orbital, parameningeal

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