Thyroglossal duct cyst: case seriesD. Tamiolakis, T.S. Chimona, E. Proimos, G. Perogamvrakis, C.E. Papadakis, G. Georgiou
Clinical case, no. 6, 2008
* Department of Ear-Nose and Throat Surgery
* Department of Pathology
Thyroglossal duct cysts most often present with a palpable (able to be felt) asymptomatic midline neck mass at or below the level of the hyoid bone. The neck mass moves with swallowing. Some patients will have neck or throat pain, or dysphagia (difficulty swallowing). The spectrum of clinical symptoms may be as varied (1).
Since the persistent duct or sinus can promote oral secretions, such cysts can become infected. Up to one half of thyroglossal cysts are not diagnosed until adult life. The tract may lie dormant for years or decades until some stimulus leads to cystic dilatation. Infection sometimes causes transient appearance of a mass or enlargement of the cyst, at times with periodic recurrences. Spontaneous drainage occurs in some instances.
TDC is most often associated with young age, two thirds of cases presenting in the first decade of life (2). The lesion usually presents as a painless swelling in the midline or paramidline of the neck. The classic description of the lesion is that of a painless swelling in a young child along the midline of the neck which rises with deglutition or tongue protrusion. The lesion is compressible and may fluctuate in size. If, however, it is entwined with the hyoid bone, it may not display any movement with tongue protrusion or swallowing (3). Definitive surgical management requires excision not only of the cyst but also of the path's tract and branches. The intimate association of the tract with hyoid bone mandates simultaneous removal of the central portion of the hyoid bone to ensure complete removal of the tract (Sistrunk procedure). Recurrence is unlikely after such an operation except with skin involvement and intraoperative cyst rupture.
This article discusses five cases of TDC which were treated in the Ear-Nose-Throat Surgery Department over a period of 11 years.
Case 1. A twenty-three year old man presented with a sinus in the region of the hyoid bone. He had noticed a submental swelling one year previously. On the basis of its clinical appearance, the lesion was diagnosed as a sinus related to a TDC. The cyst was removed via an elliptical incision in the submental region around the cyst. The tract was resected down to the hyoid bone, the central part of which was removed, but no tissue core-out was removed.
Histologically, non-specific connective tissue with muscle tissue in transverse and longitudinal sections was seen. An elliptical cystic configuration was present with a double row of cuboidal epithelial lining with a focus of intraluminal hyperplasia. Two foci of lymphoid aggregates were seen. The histopathologic diagnosis was consistent with the clinical diagnosis of TDC.
One year later, the cyst recurred as a discharging sinus from the submental wound. Another operation was performed, this time including the resection of a tract up to the base of the tongue along with the middle of the body of the hyoid bone.
The histology of this second specimen showed non-specific skeletal muscles in different sections, fat tissue, and mucous acini which collectively were not diagnostic but convincingly consistent with a clinically diagnosed TDC.
The patient was followed up for approximately two months post-surgery and no recurrence was detected.
Case 2. A 28-year-old male presented with a swelling of the neck to the left of the midline with one year duration which was growing in size. Lesion was painless. Clinical examination revealed a compressible mass 2 x 2 cm in size. The mass did not move upwards with deglutition and tongue protrusion. Differential diagnoses were TDC and branchial cleft cyst.
A fine needle aspiration was performed using a cameco syringe pistol with disposable 20cc syringe and a 23G needle. Smears showed thick, yellow, pus-like fluid with anucleate , keratinising cells, squamous epithelial cells of variable maturity including degenerate forms, and a background of neutrophils and amorphous debris. A component of epithelioid cells representing a granulomatous reaction at the edge of the cyst was seen. No atypia was seen. Neither columnar epithelial cells nor thyroid epithelial cells were recognized (fig. 1). The cytologic findings were indicative of a branchial cleft cyst and a comment was made that these features were also compatible with a TDC, and the differential diagnosis should be based on the anatomical site of the lesion.
CT section with contrast enhancement revealed an oval well-defined, well-encapsulated low-density lesion with density much lower than the surrounding muscles and being mostly that of a viscous fluid. The lesion was approximately 2 cm in size (fig. 2).
The cyst was surgically removed and followed upwards to the hyoid bone and part of it was removed with the cyst (Schlange procedure).
The histopathology report supported the diagnosis of TDC.
Case 3. A 26-year-old female presented with a painless swelling high along the midline of the neck. It had been present for six months and discharging pus for four days prior to presenting at the clinic. The lesion was clinically diagnosed as a TDC.
Orthopantomograph and CT views did not show the lesion and ultrasound imaging could only display a non-specific cystic lesion.
Under general anesthesia, the fistula was excised and a Sistrunk operation was performed.
Histologically, the sections showed fibrous connective tissue with duct-like structures lined by squamous and pseudo-stratified ciliated epithelium with moderate to severe lymphocytic infiltration around the ducts. The lining showed presence of mucous secreting cells. The histopathologic diagnosis was TDC.
At four months follow-up, no signs of recurrence could be detected.
Case 4. A 57-year-old male presented with a swelling in the left submandibular region of seven years duration which was gradually increasing in size. During the previous month, the swelling became slightly tender. Clinical examination revealed a left submandibular mass, 10 x 8 cm in diameter that was compressible. Regional lymph nodes and the overlying skin were normal. The thyroid gland was found to be normal. Intraorally, the lesion was found to be plunging into the floor of the mouth slightly raising the tongue. The teeth were found to be decayed. Medical history was unremarkable.
Orthopantomograph and posterior-anterior radiographic views of the mandible showed signs of resorption at the inferior border of the left body of mandible. Furthermore, the left side of the mandible showed a diffuse area of reduced radio-opacity when compared with the right side possibly due to a decrease in the bucco-lingual width caused by thinning of the cortical plates.
A smear of the fine needle aspiration of cyst contents showed proteinaceous material mixed with abundant aggregates of pigment-laden macrophages, neutrophils and lymphocytes. A fair number of crystals were seen. No atypical cells were seen. The diagnosis was a subacutely inflammed retention cyst.
A CT scan of the neck and mandible showed a hypodense, well-defined mostly encapsulated lesion ovoid in shape and inferior to the most inferior part of the mandible anteriorly and mostly at the level of the hyoid bone. The density of the lesion was lower than that of the surrounding muscles and was homogenous with no evidence of calcified material. No enlarged lymph nodes were seen. Thinning of the mandibular bone could be detected on both the buccal and lingual aspects. The CT report gave a diagnosis of cystic tumor of the left submandibular gland.
The patient was operated on for removal of the lesion which was found intra-operatively to be separated from the submandibular (which was found to be hypertrophic) and sublingual glands. The cyst was dissected superiorly from the floor of the mouth and inferiorly found to be attached to the hyoid bone. It was removed in one piece with the central portion of the hyoid bone. Intra- and post-operative diagnoses were TDC.
Histologically, the lesion was described as a cyst lined by squamous epithelium and pseudo-stratified columnar epithelium with hyalinization of the connective tissue wall. Focal cholesterol clefts were seen. Multinucleated giant cells were also present. The connective tissue was well vascularized with small and medium sized blood vessels. The histopathologic diagnosis was consistent with TDC.
The patient was lost for follow-up after discharge.
Case 5. A 34-year-old woman presented with a swelling in the neck to the right of the midline between the hyoid bone and thyroid cartilage which rose with tongue protrusion and deglutition. It had been present for more than one year and fluctuated in size. The clinical diagnosis was TDC.
Fine needle aspiration of the contents of the lesion yielded 3.0 ml of brown colored fluid. Microscopically, the smear showed pigment laden macrophages and lymphocytes. The appearance was compatible with a retention cyst.
A thyroid scan six days later with Tc99 revealed normal shape, size, and location of both thyroid lobes with homogenous fixation of the tracer. The swelling appeared high up in the middle of the neck and did not show any tracer uptake and had nearly disappeared after aspiration for the FNA. The scan diagnosis stated that the lesion was compatible with TDC.
Through a transverse neck incision, the strap muscles and the cystic lesion were explored. The body of the hyoid bone was removed along with the cyst and a core of tissue was removed upwards reaching the base of the tongue.
Histology of the resected lesion was that of a cyst lined by pseudostratified ciliated columnar epithelium with thyroid follicles around the cyst (fig. 3). The diagnosis was TDC.
The small number of cases of TDC which presented to our department is not surprising since this lesion is most often discovered in childhood and thus normally presents to pediatric departments. Most cases of TDC become apparent during the first decade of life (4, 5). Although it is regarded as a lesion of the young, TDC may be encountered in adults, and in the elderly. In a review of 381 case of TDC, Brown and Judd (1961), showed 28% of their patients to be above 40 years of age (6) Telander and Dean (1977) found less than 10% to occur in patients over 60 (7).
Although the cyst is classically described as a midline lesion, it may be situated lateral to the midline in 10-20% of cases (2). This range has been supported by the result of a review of 300 cases of TDC by Solomon and Rangecroft (1984) who found the lesion lateral to the midline in 16% of cases (8). In our five patients, three cysts were situated lateral to the midline, two to the left and one to the right. Deviation from the midline may be due to inflammation causing a more eccentric position or to branching remnants (9).
The vertical position of the lesion could also vary. It has been found to be intralingual in 2.1% of cases, suprahyoidal in 24.1%, thyrohyoidal in 60.9%, and suprasternal in 12.9% (1). The lesions in two of our cases (40%) were suprahyoidal while three (60%) were thyrohyoidal. We encountered no suprasternal lesions; however, it should be recognized that this does not necessarily indicate that they do not occur since lesions in this region are more likely to present to general surgery departments.
Most TDCs are asymptomatic but could be secondarily infected in an upper respiratory tract infection (10). Allard (1982) reported that inflammation was the most often mentioned initiating stimulus (1). Inflammation may lead to a rapid increase in size, cellulitis and even abscess formation (11, 12). Fistulization onto skin, as seen in two of our patients, occurs in approximately one-third of patients (1, 13). Fistulas may form as a result of spontaneous discharge following inflammation of a cyst, or after surgical intervention, or rarely as congenital fistulas. When a sinus related to a TDC is present, it is mostly in the midline and stressed with tongue protrusion. It may show discharge of cystic fluid or pus. If there is a sinus or recurrent infection related to a cervical lesion, whether in the midline or laterally placed, a TDC should be suspected. If a thickened tract from the lesion to the hyoid could be felt by palpation, the diagnosis may be confirmed. Tracing the sinus (by injection of a radiopaque dye and radiography) may lead to the foramen caecum.
The differential diagnosis of TDC includes branchial cleft and dermoid cysts. Branchial cleft cysts are usually described as located lateral to the midline and are not expected to be affected by tongue protrusion and swallowing. Discharging fistulas and aspirates of branchial cleft cysts are similar in appearance to those of TDCs. However, differentiation between the two lesions may be achieved by sinus tracking. Injection of a radiopaque dye into fistulas caused by branchial cleft cysts leads to the tonsillar fossa. Of interest to note is that a case was seen in our department in which a lesion was found in the midline of the neck of a four-year-old girl and was clinically diagnosed as TDC. However, histopathological examination of the wall of the lesion revealed numerous lymphoid follicles indicating that it was, in fact, a branchial cleft cyst. This highlights the diagnostic challenge of swellings in the neck.
Dermoid cysts, like TDCs, are generally considered to be midline lesions but may be differentiated from TDC by their consistency. They have a doughy consistency and the more complex the histologic composition, the firmer the lesions are clinically. Dermoid cysts can, like TDCs, present with a discharging sinus when infected; but when caused by the former, the sinus is more superficial and firmer. Furthermore, the aspirate of a dermoid cysts is a yellow cheesy substance which is very easily distinguished from the fluid expected from TDCs.
CT scans can be a useful aid in the diagnosis of TDCs with regard to the position and relationship to adjacent anatomical structures. The typical appearance of a TDC in a CT scan is a well circumscribed low-density lesion with peripheral rim enhancement (14). CT scanning, however, is not useful in differentiating between different types of cysts.
Delineating the different types of cysts is important since the management of TDCs requires not just simple excision but rather a Sistrunk operation which requires excision of the cyst, the central portion of the hyoid bone, and removal of a core of muscles up to the base of the tongue. Failure to do so, as in Case 1 in our report, may lead to recurrence of the cyst.
The histologic appearance of a TDC is a cyst lined by respiratory epithelium with thyroid tissue, mucous glands, and small patches of lymphoid tissue variably present in the connective tissue wall. The presence of thyroid tissue in the connective tissue wall of the cyst is considered pathognomonic of TDC, however not all specimens display such tissue. According to the literature review by Allard (1982), the frequency of cases that showed thyroid tissue ranged from 1.5% to 45% (1, 15). However, serially sectioned lesions may reveal a higher frequency of thyroid follicles (16, 17, 18).
Diagnosis of swellings in the head and neck region could present a challenge to the clinician, especially when the clinical presentation of the lesion is inconsistent with the classical description. Most cases of TDCs manifest in early childhood and thus present to pediatric departments most of the time. However, the oral and maxillofacial surgeon may also encounter such a lesion in adolescents and older patients and therefore must consider its variable presentation.
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