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Fig 20. Axial T1-weighted (A), coronal fat-suppressed T2-weighted (B), and axial contrast-enhanced fat-suppressed T1-weighted (C) MR images of a child with a lymphoma. The images show a large mass in the right posterior cervical triangle. Multiple contiguous enlarged lymph nodes are demonstrated and show trans-spatial extension (A, C) and caudal extension of involved lymph nodes in continuum (B). The postcontrast images (C) reveal peripheral enhancement of the enlarged lymph nodes with central focal areas of absent enhancement (necrosis).

Fig 21. Axial fat-suppressed T2-weighted (A), sagittal fat-suppressed T2-weighted (B), and sagittal contrast-enhanced fat-suppressed T1- weighted (C) MR images of a child with a rhabdomyosarcoma. The axial image (A) shows a large T2 hyperintense mass primary arising from the oropharynx. The surrounding cervical spaces are predominantly displaced by the mass. The sagittal T2-weighted image (B) demonstrates the extension into the nasopharynx and ethmoid sinus. Bony involvement is seen. On the contrast-enhanced image (C), relative homogenous enhancement of the lesion with some areas of focal necrosis is seen.

and is essential for precise localization and characterization of the lesions. US allows an efficient assessment of neck masses in young children and is the initial imaging technique of choice. MRI provides better detailed information of the anatomic rela- tionship and extension of these masses and can better depict the nature of solid lesions. CT scans should be used conservatively for selected, specific indications, in order to minimize ionizing radiation exposures. By taking the patient’s age and clinical history into consideration, as well as the involved anatomical cervical region, the extent of the lesion, and the characteristic imaging features, accurate definite diagnosis of neck masses can be provided. References 1. Turkington JR, Paterson A, Sweeney LE, et al. Neck masses in children. Br J Radiol 2005;78:75-85. 2. Abdel Razek AA, Gaballa G, Elhawarey G, et al. Characterization of pediatric head and neck masses with diffusion-weighted MR imaging. Eur Radiol 2009;19:201-8. 3. Gaddikeri S, Vattoth S, Gaddikeri RS, et al. Congenital cystic neck masses: embryology and imaging appearances, with clinicopatho- logical correlation. Curr Probl Diagn Radiol 2014;43:55-67. 4. Imhof H, Czerny C, Hormann M, et al. Tumors and tumor- like lesions of the neck: from childhood to adult. Eur Radiol 2004;14(Suppl 4):L155-65. 5. Lloyd C, McHugh K. The role of radiology in head and neck tumours in children. Cancer Imaging 2010;10:49-61. 6. Rosa PA, Hirsch DL, Dierks EJ. Congenital neck masses. Oral Maxillofac Surg Clin North Am 2008;20:339-52.

(nasal cavity, paranasal sinuses, nasopharynx, pterygoid fossa, middle ear), and nonparameningeal tumor site. 4,5,67 The ex- tension of disease is evaluated preoperatively as well as post- operatively and the staging system includes tumor size, nodal status, site of primary tumor, and extent of residual disease. MR imaging is the preferred imaging modality to assess the volume of the lesion, the site of origin, and the relationship of the mass to adjacent anatomical structures as well as potential intracra- nial extension. The lesion demonstrates T2 hyperintense and T1 isointense to slight hyperintense signal intensity compared to skeletal muscle. Heterogeneity of the lesion can be due to focal necrosis. There is moderate to intense enhancement on postcontrast imaging sequences (Fig 21). On diffusion-weighted MR imaging sequences, low intralesional ADC values correlate with the malignant nature of the lesion. CT may be helpful to evaluate bone involvement or destruction. The imaging stag- ing requires chest CT, abdominal US, and bone scintigraphy to search for distant metastatic disease. 1,5,67 Conclusion Congenital and acquired neck masses in the pediatric popula- tion comprise a variety of diverse conditions. By definition, con- genital anomalies are present at birth. Lymphadenitis accounts for the majority of acquired cervical masses in the pediatric age group, and therefore the bulk of acquired neck masses are be- nign lesions. Imaging plays a key role in establishing diagnosis

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