Origins and treatment of cystic lesions in the head and neck
region
EW Müller
Most cystic lesions of the head and neck region are of embryonic origin. They are usually
easily diagnosed and rarely need an additional workup. Some of these lesions may not be
symptomatic until adulthood or may not be easily recognized. Knowledge of the
embryonic origin is essential to successful treatment.
Thyroglossal cyst
Thyroglossal duct cysts (TDCs) comprise about 70% of congenital neck masses.
Embryology:
During the 4th to 7th week of embryology, the foramen caecum at the base of the tongue is
the site of thyroid development. As the tongue develops, the thyroid diverticulum
descends down into the neck, maintaining its connection to the foramen caecum. During
descent of the diverticulum, the thyroid develops and the thyroglossal duct atrophies. If
parts of the duct fail to involute, a thyroglossal cyst may develop. Secretion of the
epithelium lined remnant of the thyroglossal duct (TD) can begin anytime which explains
why only 50% of TDCs present before the age of 20yrs.
Hyoid development and descent of the thyroid occur simultaneously. The TD can be
dorsal, ventral or, most commonly, be embedded in the centre of the hyoid bone.
Since the tract never reaches the surface of the skin, thyroglossal fistulas are always
acquired, either secondary to surgery or infection.
Errors in thyroid descent can result in a lingual thyroid. Ectopic thyroid tissue can be
scattered along the whole course of the TD. A pyramidal lobe is found in about 40% due
to non resorption of the distal TD.
Clinical Presentation and Evaluation
80% of TDCs are found adjacent to the hyoid bone. They have a smooth contour and
move with swallowing or with movements of the tongue because they are attached to the
hyoid bone. Differentiation from dermoid cysts can be difficult, because they might also
be attached to the hyoid. The further differential diagnosis includes ectopic thyroid tissue,
thyroid neoplasm, submental lymphadenitis and lipoma.
Because of their communication to the base of the tongue via the foramen caecum, the
TDCs often become infected, making diagnosis and treatment more difficult.
Preoperative ultrasound is an important screening tool to demonstrate a normal thyroid
before a suspected TDC is excised. Routine preoperative hormone studies are not
necessary if the child appears clinically euthyroid. A thyroid scan is of value if the patient
is hypothyroid or the sonar fails to demonstrate a normal thyroid.
Treatment
Surgical treatment consists of en bloc cystectomy, central hyoidectomy with tract
excision up to the foramen caecum. The defect in the geniohyoid and mylohyoid muscles
is reapproximated. It is not necessary to close the defect in the hyoid bone (Sistrunk
procedure).
The operation should be done as soon as possible to avoid an intervening infection. If an
infection is already present, this should be treated with antibiotics and an abscess drained
if present. Once the inflammation has been cleared, a wide Sistrunk procedure is done
excising the distorted edges of the cyst.
Recurrent disease is attributed to incomplete resection either of the central part of the
hyoid or the central stalk leading to the foramen caecum. It shows usually within a year
after primary resection. Clinically it presents as an infection in the region of the previous
excision. Unfortunately, the recurrence rate after secondary TDC excision is as high as
25%.
Thyroglossal duct papillary carcinoma is not seen in children, but can occur in adults.
Controversy exists whether a Sistrunk operation suffices in these cases or if a total
thyroidectomy should be added.
Anomalies of the Branchial Clefts
Branchial anomalies contribute 30% of the congenital neck masses and can present as
fistulas, sinuses or cysts. Cysts present later than the other abnormalities. Complete
fistulas are more common than sinuses and during childhood both are more common than
cysts.
Embryology:
By the end of the fourth week of gestation, four well defined arches (and two rudimentary
arches) have been formed in the lower face and neck region of the embryo. These are
lined externally by ectoderm, internally by endoderm, with mesoderm in between. Each
arch is separated by clefts externally and pouches internally. In fish these structures form
gills, but in humans these clefts and pouches are gradually obliterated to form head and
neck structures. Branchial anomalies result from incomplete obliteration of the clefts and
pouches.
As the embryo grows, the arches coalesce and obliterate all the clefts except for a portion of the first, which becomes
the eustachian tube and the auditory canal (Fig. 19-1). The first branchial arch forms the mandible and contributes to
the maxillary process of the upper jaw. Abnormal development of this arch results in a wide range of facial deformities,
including cleft lip and palate, an abnormal shape or contour of the external ear, and malformed internal ossicles.
The second branchial arch forms the palatine tonsil, the tonsillar fossa, and the hyoid bone. The most common
branchial abnormalities (90%) arise from the second cleft. These abnormalities are thought to be due to incomplete
obliteration as the first arch overgrows the second, third, and fourth clefts and fuses with the lateral branchial wall.
The third arch gives rise to the inferior parathyroid glands and the thymus (Fig. 19-1).
The fourth branchial arch forms the superior parathyroid glands and the ultimobranchial body, which is responsible for
development of the thyrocalcitonin-producing parafollicular cells of the thyroid gland. Anomalies of the third and
fourth clefts and pouches are rare.
Clinical presentation:
Cleft anomalies can present as cysts, sinuses or fistulae. When a sinus is present, the
diagnosis is made in childhood. If no external opening exists, the diagnosis might be
delayed until adolescence or adulthood.
An external sinus is located at the anterior
border of the sternocleidomastoideus
(SCM) muscle secreting clear mucoid
fluid. The diagnosis is often apparent on
examination rendering further special
examinations unnecessary.
Branchial cleft cysts present high in the neck as a palpable lesion deep to the SCM
muscle between the bifurcation of the carotid artery. They might be confused with
lymphangiomas, haemangiomas, lymphadenopathy and metastatic tumors.
Branchial cleft cysts can become secondarily infected and this can be the first sign
alerting the physician of its presence.
Diagnosis:
Sonar is very helpful showing the typical position of these lesions and separating cystic
from solid lesions. If necessary further examinations may help (CT, MRI, FNA),
especially with solid masses.
Treatment:
The definitive treatment of these abnormalities is surgical excision. Unresected cysts and
sinuses have a high risk for infection. Surgery in infants is delayed until age 3 to 6
months of age to minimize the risk associated with anaesthesia, in older individuals the
surgery is done as soon as conveniently possible. As with thyroglossal cysts, acute
infections should first be treated with antibiotics, needle aspiration or with incision and
drainage followed with complete excision after resolution of the infection.
Lymphangiomas
Lymphangiomas can arise anywhere in the body, but their preferred site is the head and
neck region (50%). They present at birth or in early childhood; 90% are diagnosed before
the age of 2 years.
Embryology:
Lymphangiomas are lymphatic cysts that have become isolated during embryological
development and fail to drain into the venous system.
Clinical presentation and evaluation:
Most lymphangiomas present as a painless cystic mass or diffuse swelling which grows
slowly with the child. Upper respiratory tract infections or trauma may enlarge the mass
or worsen the swelling. In a few patients this requires intervention to secure the airway.
History and physical findings strongly suggest the diagnosis in about half of the patients.
In the other cases, it is necessary to differentiate from other cystic lesions occurring in
this region. CT and US confirm the cystic nature of the lymphangioma. MRI is best in
evaluating the extent and relationship to other structures of the neck. Needle aspiration
helps to differentiate lymphangiomas from other fluid filled masses.
Types:
Lymphangiomas are classified as macrocystic or microcystic. The macrocystic type
consists of cysts bigger than 1cm and contains less than 5 cysts; in the microcystic type
there are more than 5 cysts and/or they are smaller than 1 cm.
Treatment:
Two main treatment modalities exist: Surgical excision and injection therapy with
sclerosing agents.
The different sclerosing agents (Bleomycin, alcohol, tetracycline, etc.) are probably
equally efficacious. OK-432, which is a lyophilized extract of Streptococcus pyogenes, is
said to cause less perilesional fibrosis than other agents. Injection therapy works well for
the macrocystic types, but unfortunately, these types are not very common.
Surgery is more efficient in the treatment of lymphangiomas than the sclerosing agents,
especially in the microcystic types, but can cause serious complications, especially
injuries to important anatomical structures.
Treatment: Microcystic lesions should be treated surgically. Macrocystic lesions respond
well to sclerosing agents. Lymphangiomas expected to be difficult to excise can be
pretreated with sclerosing agents to achieve shrinkage and then excised.
Dermoid and Epidermoid Cysts
Dermoid and epidermoid cysts result from entrapment of epithelial elements along
embryonic lines of fusion and contain endodermal and ectodermal elements. Dermoids
are differentiated from epidermoids histologically by the accessory glandular structures
found in dermoids. Dermoids contain sebaceous glands, hair follicles and connective
tissues. Both contain sebaceous material within the cyst cavity which accumulates with
time and causes the cyst to increase in size.
The presentation of dermoid cysts is usually typical clinically. The most common
location for dermoid cysts in children is along the supraorbital palpebral ridge. This
lesion appears as a characteristic swelling in the corner of the eyebrow which moves with
the skin.
Other locations are in the midline of the neck close to the hyoid. In this case they might
move with swallowing or tongue protrusion leading to confusion with thyroglossal duct
cysts. They are, however, more superficial and lack a connection with the hyoid bone.
Midline scalp lesions should be evaluated for intracranial extension (US, CT, MRI)
before excision.
Treatment is by complete surgical excision. The rate of recurrence is increased by
incomplete resection or intraoperative rupture.
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