2017 Sec 1 Green Book

Fig 10. Axial (A), coronal (B), and sagittal (C) CT images in soft tissue window of a child with cervical extension of a bronchogenic cyst. The images show a well-defined cystic structure (A-C) in the sternal notch region (C). The predominant volume of the cystic structure is found in the upper thoracic region (B, C) and therefore the cervical part of the lesion presumably represents cervical extension of a thoracic bronchogenic cyst.

Fig 11. Axial T2-weighted (A) and sagittal T1-weighted (B) fetal MR images of a fetus with a large cervical teratoma. The axial image (A) shows a large right-sided neck lesion with widespread infiltrative extension. The cystic components are T2 hyperintense. The sagittal image (B) demonstrates the typical area of fat as T1 hyperintense signal intensity (arrow). Polyhydramnios is noted and is due to impaired fetal swallowing. The postnatal CT image (C) of the child shows the calcification / ossification in the lesion.

Congenital and Acquired Vascular Masses Vascular Malformations Vascular malformations include several types of anomalies and are identified in the head and neck region in 1–4% of the pediatric population. They demonstrate normal endothe- lial cell turnover and are classified as nonneoplastic lesions according to the International Society for the Study of Vas- cular Anomalies (ISSVA) classification system recently up- dated in 2014 (Table 2), which stems from the early work of Mulliken and Glowacki. 34 Vascular malformations may remain stable, grow commensurate to the child, or demon- strate enlargement after infection, trauma, or endocrine changes (eg, puberty, pregnancy). Vascular malformations are grouped based on the predominant anomalous tissue or vessel type into lymphatic malformations, venous malformations, arteri- ovenous malformations (AVMs), capillary malformations, and mixed-type lesions. 35,36 The capillary malformations (previ- ously named as port wine stain) are rather cutaneous le- sions than a neck mass, therefore are beyond the scope of this review. Lymphatic malformations are the most common congenital anomalies in the posterior cervical triangle accounting for 75–80% of the cystic lesions in this region, but they can occur in any of the different neck regions. The majority of these lesions are present at birth or appear before the age of 2 years as a soft mass of variable size. 3 Lymphatic malformations can be

three embryonic cell layers involving endodermal, mesoder- mal, and/or ectodermal elements. They are hypothesized to arise either from pluripotent stem cells sequestered during em- bryogenesis or from embryonic tissue that escaped the regional influences of the primary organizer. 6 Teratomas are classified as mature or immature lesions. 18,32 The risk of malignant con- genital cervical teratomas increases with advanced age at di- agnosis. Alpha-fetoprotein (AFP) is an indicator for teratoma in infants and children; however, in neonates, AFP has high normal baseline values. Cervical teratomas typically are lo- cated in the midline in the suprahyoid region. 1,32 They may extend into the mediastinum or compress the trachea. If tra- cheal compression occurs during embryonic development, this may result in pulmonary hypoplasia. In prenatally identified lesions, polyhydramnios may be seen secondary to impaired fetal swallowing. 32 On US, the lesion shows heterogeneous echogenicity with solid and cystic components. MR imaging demonstrates the typical areas of fat as T1 hyperintense signal intensity. The cystic components are T2 hyperintense. Intrale- sional calcifications can be identified on susceptibility-weighted MR imaging sequences or on selective CT examinations. At time of diagnosis, cervical teratomas are often large lesions with widespread infiltrative extension. 1,5 There are no reliable imag- ing features to differentiate mature from immature teratomas. On histology, these lesions tend to be generally benign mature tumors. 33 Immature cervical teratoma or malignant transforma- tion is rare.

178