patient group. However, CT occasionally is contributive as a
fast and readily available imaging technique in the emergency
setting, and is helpful for lesions that involve bony structures
and for the acute diagnostic work-up of infections/abscesses
in the neck according to the American College of Radiology
(ACR) Appropriateness Criteria.
9
Basic knowledge of the normal contents of each anatomi-
cal space is essential in evaluating the various pathologies and
masses that can arise within each space.
The goal of this review is to identify the characteristic lo-
cation and imaging features, differential diagnosis, and dif-
ferentiating features of the most frequent congenital and ac-
quired cervical mass lesions (lumps and bumps) in the pediatric
population.
Congenital Cystic Masses
Thyroglossal Duct Anomalies
Thyroglossal duct remnants are reported in 7% of the
population.
10
These anomalies are the most common congen-
ital anomalies of the neck, representing 70% of the congenital
neck masses (second most common neck mass after cervical
adenopathy in the pediatric age group).
6
The formation of the
thyroid gland begins with an endodermal thickening in the floor
of the primitive pharynx-tuberculum impar in the third embry-
onic week. From this site, the thyroid diverticulum develops
and its opening forms the foramen cecum. Due to progressive
growth/elongation of the embryo, the diverticulum descends
caudally into the neck and forms the thyroglossal duct. This
duct is a temporary structure coursing from the foramen ce-
cum at the tongue base, descending in the anterior midline,
looping posterior to the hyoid bone, and continuing its descent
anterior to the thyrohyoid cartilage and trachea to the level of
the thyroid. The descent of the thyroglossal duct occurs before
formation of the hyoid bone, and therefore remnants of the
duct can become trapped within the hyoid bone.
6,11
The duct
generally involutes around gestational week 8–10.
Thyroglossal duct cysts are diagnosed in 40% of surgically
removed neck masses in the pediatric population.
6
The lesion
manifests from infancy until young adulthood. Thyroglossal
duct cysts are often asymptomatic until enlargement or inflam-
mation occurs associated with infection or trauma. The cyst
arises from a remnant of the thyroglossal duct. Any portion of
the duct, from the foramen caecum to the pyramidal lobe of the
thyroid gland, may persist and cause cyst formation due to se-
cretions from the epithelial lining of the duct.
1,12
In pathologic
specimens of excised thyroglossal duct cysts, thyroid tissue is
reported in up to 62% of cases.
13
As a result of the course of the
duct, thyroglossal duct cysts are primarily located in the mid-
line (75%) or just off-midline (25%). Paramedian location occurs
more often on the left. The vast majority of the cysts are located
at or about the level of the hyoid bone, and a minority has an
infrahyoid position or is located in the suprahyoid neck.
1,3
The
thyroglossal duct cysts located at the level of the tongue base
can be difficult to differentiate from vallecular cyst occurring
at the exact same location based on imaging appearance alone.
The imaging features of thyroglossal duct cysts comprise a well-
defined, thin-walled cystic structure in the typical midline or
paramidline location. Heterogeneous cyst content may reflect
proteinaceous material/hemorrhage or infection as evidenced
by debris and fluid levels both on US and MR imaging. In par-
ticular, T1 hyperintensity may indicate prior hemorrhage, and
this can be further verified with SWI. Noncomplicated cysts do
not demonstrate wall thickening or postcontrast enhancement
(Fig 1). The cyst wall thickness and degree of contrast enhance-
ment of the cyst wall may vary with inflammation/infection. US
enables dynamic evaluation, a characteristic imaging upward
movement of the cyst with tongue protrusion or swallowing
due to the origin of the duct at the foramen cecum is typically
observed.
12
The majority of the cysts show a close relation to
the hyoid bone. At the level of the hyoid bone, the cyst may
demonstrate a tail “diving” into the hyoid bone, reflecting en-
trapment of duct remnants in the hyoid bone. To minimize the
risk of recurrence after resection, removal of the central portion
of the hyoid bone is typically included in the
curative
excision
of the cyst and/or sinus tract (eg, Sistrunk procedure, modified
Sistrunk procedures).
14
Factors influencing the recurrence rate
after the Sistrunk procedure (2.6%) are, eg, postoperative infec-
tion, the presence of multiple tracts and distorted anatomy due
to preoperative infection.
15,16
Infrahyoid cysts favor an off-midline position, deep to or
embedded within the strap muscles (Fig 2) with a tail toward the
midline (Fig 2).
3
Evaluation of the presence of a normal thyroid
gland in the normal location is important in the preoperative
Fig 1.
Sagittal contrast-enhanced T1-weighted (A) and sagittal fat-suppressed T2-weighted (B) MR images of a child with a suprahyoid
thyroglossal duct cyst. The images reveal a well-defined, thin-walled cystic structure in the typical midline location at the level of the foramen
cecum at the tongue base. No cyst wall enhancement is encountered on postcontrast imaging. Differentiation between a thyroglossal duct cyst
located at the tongue base and a vallecular cyst is not possible based on imaging appearance alone.
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