A 45-year-old man presents to his primary care physician complaining of gradual swelling in the anterior area of his neck over the past 6 months. He has not experienced any pain in the swollen area. He additionally denies any difficulty in swallowing or problems with breathing. There is no history of trauma, fever, or any alteration of his voice. He also denies any significant personal or family medical history, and he states that he currently takes no medications.
An ultrasound of the neck is obtained (Image 1). As a follow-up, a computed tomography (CT) scan of the neck is also performed (Image 2).
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HINT
This is the most common etiology for a midline neck mass.
Authors:
Pramod Gupta, MD, Staff Physician, Department of Radiology, Dallas VA Medical Center, Dallas, Texas
Jitendra Gohil, MD, Staff Physician, Department of Radiology, Dallas VA Medical Center, Dallas, Texas
eMedicine Editors:
Michael J. Rest, MD, Resident Physician, Department of Emergency Medicine, Yale-New Haven Hospital, New Haven, Conn
Rick G. Kulkarni, MD, Assistant Professor, Yale School of Medicine, Section of Emergency Medicine, Department of Surgery, Attending Physician, Medical Director, Department of Emergency Services, Yale-New Haven Hospital, Conn
Prajoy Kadkade, MD, FACS, Assistant Professor of Otolaryngology, Department of Otolaryngology, North Shore – Long Island Jewish Hospital System
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ANSWER
Thyroglossal duct cyst: The ultrasound image (Image 1) shows a large cystic mass anterior to the thyroid gland (arrowheads). The contrast-enhanced CT scan demonstrates the same predominantly midline cystic mass extending anteriorly to the thyroid gland and under the strap muscles, without evidence of ectopic thyroid tissue. The findings are consistent with the diagnosis of a thyroglossal duct cyst, the most common etiology for a midline neck mass. Thyroglossal duct cysts usually occur between the hyoid bone and the thyroid gland. They represent up to 70% of congenital neck anomalies and are the second most common cause of neck masses (after lymphadenopathy).
Thyroglossal duct cysts usually appear in the midline and can be present anywhere along the line of descent in fetal development of the thyroid gland, from the foramen cecum at the level of the base of the tongue to the level of the thyroid gland. From an embryologic perspective, the thyroid gland develops during the third week of life as an outgrowth of the floor of the primitive pharynx. The primitive thyroid then descends through the thyroglossal duct from the foramen cecum to its mature position in the anterior neck. The thyroglossal duct is normally resorbed by 7-10 weeks of fetal life. Abnormal persistence of the thyroglossal tract, accompanied by mucus production from the endothelial lining of the tract, leads to the development of a thyroglossal duct cyst. Approximately 7% of the population has thyroglossal duct remnants, and the distributions are equal in males and females. The cysts are usually found in children or in adults younger than 30 years, but they can develop in adults of any age. There are 4 general types of thyroglossal duct cysts: thyrohyoid cysts (61% of cases), suprahyoid cysts (24%), suprasternal cysts (13%), and intralingual cysts (2%).
The differential of neck masses can be categorized by the location of the mass itself; the usual categorization is between lateral and midline masses. The most frequent causes of lateral masses are lymphadenopathy, branchial cleft cyst malignancy, cystic lymphangioma, and dermoid and teratoid cysts. While thyroglossal duct cysts are the most common etiology for midline masses, the differential also includes dermoid and teratoid cysts, ectopic thyroid tissue, malignancy, and cystic lymphangioma. On radiologic images, a thyroglossal duct cyst appears as a cyst-like mass along the course of the thyroglossal duct. It must be differentiated from dermoid cysts and lymphangiomas; a dermoid cyst usually contains fat, and lymphangioma is most common in infancy or early childhood and usually occurs in the posterior triangle of the neck behind the sternocleidomastoid muscle.
The diagnosis of thyroglossal duct cysts is made on the basis of history and confirmed with diagnostic imaging. Most patients with thyroglossal duct cysts present with either a history of a slowly growing asymptomatic mass or a history of a relatively rapidly growing mass, if the cyst is infected in the anterior midline of the neck. Frequently, the swelling is exacerbated during an upper respiratory infection. The pathognomonic sign of thyroglossal duct cysts is that they move with swallowing and with protrusion of the tongue, although the mobility of larger cysts may be restricted. Imaging studies, including ultrasonography and CT of the neck, will confirm the diagnosis and ensure the presence of a normal, separate thyroid gland. Thyroid function tests should be obtained to confirm normal thyroid function. If imaging reveals the absence of a thyroid gland, but normal thyroid function is noted on tests, surgical management should be deferred because the thyroglossal duct cyst may represent the only thyroid tissue found in that patient.
Once diagnosed, thyroglossal duct cysts are removed because they have the potential to become infected and undergo malignant transformation and they are cosmetically undesirable. The treatment of choice is the Sistrunk procedure, named after Dr. Walter Ellis Sistrunk and first described in 1920. The procedure, rather than simply excising the cyst, involves dissecting the central portion of the hyoid bone and extension of the excision to a small block of muscle around the foramen cecum at the base of the tongue. The recurrence rate associated with simple excision of a thyroglossal duct cyst is approximately 50%, whereas the recurrence rate associated with a formal Sistrunk procedure is approximately 5%. If the cyst is infected at the time of diagnosis, treatment with antibiotics (such as ampicillin/sulbactam, amoxicillin/clavulanate, or clindamycin) is indicated prior to surgical excision.
The most common complication of thyroglossal duct cysts is infection with the possibility for abscess formation, spontaneous rupture, and formation of a secondary sinus tract. A Sistrunk procedure mistakenly performed for thyroid ectopia that removes thyroid tissue can cause hypothyroidism. Infrequently, the cysts can compress the trachea and lead to respiratory distress, especially if they are rapidly expanding. Carcinoma is the most feared complication, occurring in about 1% of all cases, with papillary carcinoma accounting for 85-92% of malignancies and follicular carcinoma accounting for the rest. Most patients who develop carcinoma tend to present at a later age. Definitive management of thyroglossal duct carcinoma includes excision of the cyst, often with thyroidectomy, and subsequent radioiodine ablation treatment.
Since the patient in our case presented with a clinically noninfected thyroglossal duct cyst, he was not given antibiotics. He underwent an elective Sistrunk procedure and was discharged from the hospital the following day without complications.
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