Cystic neck masses: A pictorial review - Applied Radiology Online

Cystic neck masses: A pictorial
review of unusual presentations
and complicating features
Francie Masters, MD, and Curtis A. Given II, MD
Imaging plays a vital role in the evaluation
of cystic neck masses. To aid in
the correct preoperative diagnosis
and to facilitate appropriate medical
management, it is important for radiologists
to recognize both the common and
the unusual manifestations of these
lesions. This pictorial review illustrates
the typical appearance of cystic neck
masses and the more unusual, uncommon
presentations and complications.
Thyroglossal duct dyst
The thyroglossal duct cyst (TDC) is
the most common congenital neck mass,
compromising 70% of all congenital
neck anomalies. 1 The thyroid normally
descends along the thyro glossal duct,
extending from the foramen cecum,
through the floor of the mouth, and
passes anterior to the hyoid bone, to its
final position within the inferior neck.
The duct normally involutes during ges-
Dr. Masters is a Radiology Resident and
Dr. Given is an Associate Professor of
Radiology, Department of Radiology,
University of Kentucky Chandler Medical
Center, Lexington, KY.
Portions of this material were presented as
a Scientific Exhibit at the American Society
of Neuroradiology (ASNR) Annual
Meeting, June 2007, Chicago, IL.
26 ■ APPLIED RADIOLOGY ©
tation, but if any portion of the duct persists
it can give rise to a TDC. The thyroglossal
duct is intimately associated
with the hyoid bone (Figure 1) and often
passes directly through it. 2 Clinically,
TDCs may migrate cephalad with protrusion
of the tongue. 2
On all imaging modalities, TDCs
appear as cystlike masses of the anterior
neck, at the level of the hyoid bone or
within the strap muscles (Figures 1
through 3). Approximately 75% percent
of all TDCs are located in the midline,
with 25% within 2 cm of midline. 3 With
imaging, TDCs generally appear as
smooth, well-circumscribed lesions containing
simple fluid. Thyroglossal duct
cysts may exhibit peripheral enhancement
following intravenous contrast
administration. With recurrent inflammation,
the cysts may become more heterogeneous
in appearance and develop
internal septations (Figure 2).
Roughly 1% of TDCs are associated
with thyroid carcinoma, most commonly
of the papillary subtype. 1,3,4 When
there are solid soft tissue elements associated
with a TDC, often a nodular
focus of solid tissue within the dominant
cyst (Figure 3), carcinomas arising
within TDCs may be suspected. 4,5 Carcinomas
may also be seen as purely
solid masses along the course of the
thyroglossal duct. Calcification with the
cyst is thought to be a specific finding of
carcinoma within a TDC 4,5 (Figure 3). In
contrast to their traditional counterparts
in the thyroid gland, carcinomas arising
within TDCs rarely metastasize to cervical
lymph nodes. 1,4 However, the presence
of carcinoma in a TDC may
indicate the need for an additional thyroidectomy,
6 as up to 14% of patients
will have a coincident microscopic
focus of papillary carcinoma within the
thyroid gland. 7
Branchial cleft cysts
Branchial cleft cysts (BCC) arise
from incomplete obliteration of any
branchial tract, resulting in either a cyst
(75%) or sinus tract (25%). 8 Second
branchial cleft anomalies comprise 95%
of all branchial cleft lesions, classically
presenting as cystic masses at the anterolateral
border of the sterno cleidomastoid
muscle, lateral to the carotid
space and at the posterior margin of the
submandibular gland (Figure 4). Less
common branchial cleft anomalies
include a first BCC, or a parotid lymphoepithelial
cyst, arising from a tract
extending from the external auditory
canal through the parotid to the submandibular
triangle (Figure 5). Third
and fourth BCCs are exceedingly rare.
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A B
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CYSTIC NECK MASSES
FIGURE 1. Thyroglossal duct cyst. (A and B) Axial contrast-enhanced CT images show a cystic mass (arrows) associated with the hyoid bone
(arrowhead in A) and embedded with the strap muscles.
A B
FIGURE 2. Infected thyroglossal duct cyst. (A) A transverse sonographic image reveals a midline cystic neck mass with internal septations
(arrows). (B) An axial contrast-enhanced CT image shows the mass embedded within the strap muscles and depicts surrounding inflammatory
change (arrowheads).
A B
FIGURE 3. Papillary carcinoma arising within a thyroglossal duct cyst. (A) Axial and (B) sagittal
reformatted enhanced CT images reveal a complex cystic anterior neck mass associated
with the hyoid bone and embedded within the strap muscles. Within the cystic mass, there is a
soft tissue nodule that contains small areas of calcification (arrows).
FIGURE 4. Second branchial cleft cyst. This
axial contrast-enhanced CT image shows a
cystic mass (arrow) with a thin rim of en hance -
ment displacing the submandibular gland
(arrowhead) anteriorly and the sternocleidomastoid
muscle posteriorly (asterisk).
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CYSTIC NECK MASSES
A B
FIGURE 5. First branchial cleft cyst. (A and B) Axial short tau inversion recovery MR images show a cystic lesion within the posterior aspects of
the parotid gland (arrowheads) with a small fistulous tract extending toward the external auditory canal (arrow in A).
FIGURE 6. Infected second branchial cleft cyst. This
axial contrast-enhanced CT image shows a cystic mass
(arrow) with a thin rim of enhancement displacing the
submandibular gland anteriorly with surrounding inflammatory
change (arrowheads).
A B
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FIGURE 7. Presumed primary carcinoma arising within a second branchial cleft
cyst. An axial contrast-enhanced CT image reveals a cystic mass posterior to the
submandibular gland with eccentric enhancing soft tissue (arrow) along the posterior/medial
wall. After a 13-month follow-up period, no additional malignancies or
sites of tumor have been identified.
FIGURE 8. Plunging ranula. Axial contrast-enhanced CT images show a cystic mass centered within the submandibular space. A characteristic
“tail sign” is present (arrow in A), with tapering of the lesion anteriorly into the sublingual space.
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CYSTIC NECK MASSES
FIGURE 9. Dissecting ranula. (A and B) Axial short tau inversion recovery MR images show a
cystic mass centered within the left sublingual space with a small component tapering anteriorly
into the sublingual space (tail sign). The ranula has dissected across the midline into the
left sublingual space (arrow in A).
A
B
A B
FIGURE 10. Infected ranula extending into the parapharyngeal space. (A) Serial axial and
(B and C) oblique sagittal reformatted contrast-enhanced CT images show a cystic mass
(arrows) within the left sublingual space extending posteriorly and superiorly through the parapharyngeal
space. There is extensive inflammatory change and reactive lymphadenopathy.
30 ■ APPLIED RADIOLOGY ©
C
FIGURE 11. Cystic hygroma. Axial (A) T1weighted
and (B) short tau inversion recovery
images show an infiltrative, multiseptated
lesion throughout the deep fascial planes of
the neck. (A) The variable signal seen on the
T1-weighted image is indicative of prior hemorrhage.
Third BCCs are posterior to the common
or internal carotid artery and the sternocleidomastoid
muscle, between the
hypoglossal nerve below and the glossopharyngeal
nerve above. 9 Fourth BCCs
are generally sinus tracts or fistulas and
arise from the pyriform sinus, pierce the
thyrohyoid membrane, and descend
along the tracheoesophageal groove.
Branchial cleft cysts may become
infected and exhibit thickening and
enhancement of the cyst wall (Figure 6),
mimicking a suppurative lymph node.
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A
B

A B
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CYSTIC NECK MASSES
FIGURE 12. Infected lymphangioma. (A and B) Axial contrast-enhanced CT images of the neck reveal an infiltrative, multilocular cystic lesion of the
left posterior triangle. The significant surrounding edema and inflammatory change (arrows) indicate a superimposed infection.
A B C
FIGURE 14. Mixed laryngocele. This axial
contrast-enhanced CT image shows a dilated,
air-filled sac with a small air-fluid level. There
is both a dilated internal component (saccule,
arrowhead) and a dilated extralaryngeal component
(arrow) extending through the thyrohyoid
membrane.
The existence of a primary carcinoma
(Figure 7) arising within a BCC
remains controversial. Most suspected
cases are likely metastatic lesions from
occult primaries. Imaging is generally
insufficient to differentiate cystic nodal
metastases from primary branchiogenic
A
carcinomas, with both exhibiting soft
tissue components associated with a
cystic lesion. Khafif 10 proposed that to
make a diagnosis of a primary carci-
FIGURE 13. Floor of mouth dermoid cyst. (A and B) Axial
and (C) sagittal reformatted contrast-enhanced CT
images reveal a cystic midline floor-of-mouth mass with
several discrete foci of fat density (arrows) layering in the
nondependent portion of the lesion, giving a “sac of marbles”
appearance.
FIGURE 15. Bilateral laryngoceles associated with laryngeal carcinoma. (A and B) Axial
contrast-enhanced CT images show bilateral laryngoceles (mixed on the left side) associated
with a bulky left-sided supraglottic squamous cell carcinoma (arrows in B).
B
noma within a BCC there must be no
identifiable primary carcinoma elsewhere,
and that the cystic lesion must
show transition from normal epithelium
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CYSTIC NECK MASSES
A B
FIGURE 16. Laryngopyocele. (A) Serial axial and (B) coronal reformatted contrast-enhanced CT images of the neck show a large cystic mass
(arrowheads) with an irregular rim of enhancement and surrounding inflammatory change. The mass is centered within the paraglottic space,
with extra laryngeal extension through the thryohyoid membrane. A small “neck” of the lesion that can be seen coursing through the paraglottic
fat represents the nondilated saccule (arrows).
A B
FIGURE 17. Thymic cyst. (A) Axial and (B) coronal reformatted noncontrastenhanced
CT images of the neck show a large cystic mass (arrows) that is posterior
to the sternocleidomastoid muscle and extends from the left anterior neck into
the upper mediastinum. There is mass effect and displacement of the airway.
to invasive carcinoma (transitional zone)
on cytopathologic analysis.
Ranulas
Ranulas represent cystic lesions of the
floor of mouth, usually occurring secondary
to obstruction of the sublingual
duct. Ranulas are classified as either
“simple” and confined to the sublingual
32 ■ APPLIED RADIOLOGY ©
space, or as “plunging” with extension
through the floor of mouth and below the
mylohyoid muscle. The plunging variety
presents as a cystic mass centered within
the submandibular space (Figure 8).
Rarely, ranulas can dissect across the
midline between the mylohyoid and
geniohyoid muscles to present as a bilateral
mass (Figure 9). Ranulas may
become infected and demonstrate a
thick, irregular rim of enhancement
with surrounding inflammatory change
(Figure 10). Because of the lack of a fascial
boundary between the sublingual/
submandibular and the parapharyngeal
spaces, plunging ranulas may uncommonly
extend into the parapharyngeal
space 11 (Figure 10).
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CYSTIC NECK MASSES
Cystic hygroma
Cystic hygromas represent the most
common form of a lymphangioma.
These lesions are thought to arise from
an early sequestration of embryonic
lymphatic channels, 12 most commonly
occurring along the developing jugular
chain. Cystic hygromas typically appear
as a multilocular cystic mass with septations
of variable thickness, usually centered
in the posterior triangle or submandibular
space. These lesions are
characteristically infiltrative in nature
and do not respect fascial planes (Figure
11). Fluid-fluid levels may be present
when the lesions are complicated by
hemorrhage, and large lesions may cross
the midline (Figure 11). Cystic hygromas
may become infected and increase
in size (Figure 12).
Dermoid and epidermoid cysts
Dermoid and epidermoid cysts may
occur anywhere in the body, with 7% presenting
as head and neck lesions, most
commonly lateral to the eyebrow. 9 Approximately
11% of the head and neck
lesions are located within the floor of the
mouth. 9 The floor-of-the-mouth lesions
typically present as thin-walled, unilocular
masses located in the submandibular
or sublingual space. There may be coalescence
of fat into small nodules within the
cystic lesion, giving a “sac-of-marbles”
appearance (Figure 13). The rim of the
cyst may show contrast enhancement. It
has been noted that 5% of lesions may
undergo malignant degeneration into
squamous cell carcinomas. 13
Laryngocele
The laryngeal ventricle is a slitlike
cavity, with the orifice located between
the true and false cords. A laryngocele
is dilatation of the laryngeal saccule, a
small pouch arising from the roof of
the ventricle. 14 Laryngoceles confined
to the larynx are known as internal
34 ■ APPLIED RADIOLOGY ©
laryngoceles. Those that extend through
the thyrohyoid membrane, but with dilation
of only the extralaryngeal component
are termed external. Mixed
laryngoceles have dilatation of the saccule
on both sides of the thyro hyoid
membrane (Figure 14).
Laryngoceles generally present as
round or oval lesions within the superior
paralaryngeal space (Figure 14) and
may have an extralaryngeal component
(external and mixed). The laryngocele
may be completely air-filled, fluid-filled,
or have an air-fluid level (Figure 14).
Fifteen percent of laryngoceles are associated
with carcinoma, 15 with tumor
occluding the orifice of the laryngeal
ventricle (Figure 15). The presence of
soft tissue within a laryngocele suggests
an underlying neoplasm. In as many as
8% to 10% of cases, 16 a laryngocele may
become infected, called a laryngopyocele
(Figure 16).
Thymic cyst
Thymic cysts have a disputed etiology,
but most favor the theory that these
lesions arise from persistence of the thymo
pharyngeal duct, 17 adjacent to the
carotid sheath from the angle of the
mandible to the thoracic inlet. 18 The
cysts arise from the third and fourth
branchial clefts, and, therefore, thymic
cysts may have a similar appearance to
third and fourth branchial cleft cysts,
being differentiated only by the presence
of thymic tissue within thymic cysts.
The cysts usually present as a unilocular
cystic mass extending inferiorly within
the neck, paralleling the sternocleidomastoid
muscle (Figure 17). There are
no reports of myasthenia gravis or neoplasia
associated with thymic cysts. 9
Conclusion
Patients with palpable neck masses are
frequently sent for evaluation with crosssection
imaging both for diagnosis and for
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planning biopsy or surgical resection. It is
important for radiologists to not only recognize
the common appearance of cystic
neck masses, but to appreciate the more
unusual manifestations of such masses
and potential complications that may alter
therapy or surgical management.
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