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a closed sac that develops abnormally in some body structure

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胞嚢(ほうのう)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/14 07:19:26」(JST)

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A thyroglossal cyst is a fibrous cyst that forms from a persistent thyroglossal duct.

Presentation

It usually presents as a midline neck lump (in the region of the hyoid bone) that is usually painless, smooth and cystic, if infected pain can occur. There may be difficulty breathing, dysphagia (difficulty swallowing), and/or dyspepsia (discomfort in the upper abdomen), especially if the lump becomes large.

The most common locations for a thyroglossal cyst is midline or slightly off midline, between the isthmus of the thyroid and the hyoid bone or just above the hyoid bone. A thyroglossal cyst can develop anywhere along a thyroglossal duct, though cysts within the tongue or in the floor of the mouth are rare.

A thyroglossal cyst will move upwards with protrusion of the tongue.

Thyroglossal cysts are associated with an increased incidence of ectopic thyroid tissue. Occasionally, a lingual thyroid can be seen as a flattened strawberry-like lump at the base of the tongue.^[1]

Embryology

The thyroglossal tract arises from the foramen cecum at the junction of the anterior two-thirds and posterior one-third of the tongue. Any part of the tract can persist causing a sinus, fistula or cyst. Most fistulae are acquired following rupture or incision of the infected thyroglossal cyst. A thyroglossal cyst is lined by pseudostratified, ciliated columnar epithelium while a thyroglossal fistula is lined by columnar epithelium.

Symptoms

Thyroglossal duct cysts most often present with a palpable (able to be felt) asymptomatic midline neck mass below the level of the hyoid bone. The mass on the neck moves during swallowing or on protrusion of the tongue because of its attachment to the tongue via the tract of thyroid descent. Some patients will have neck or throat pain, or dysphagia.

The persistent duct or sinus can promote oral secretions, which may cause cysts to become infected. Up to half of thyroglossal cysts are not diagnosed until adult life. The tract can lie dormant for years or even decades until some kind of stimulus leads to cystic dilation. Infection can sometimes cause the transient appearance of a mass or enlargement of the cyst, at times with periodic recurrences. Spontaneous drainage may also occur. Differential diagnosis are ectopic thyroid, enlarged lymph nodes, dermoid cysts and goiter.

Clinical features

Clinical features can be found in the subhyoid portion of the tract and 75% present as midline swellings. The remainder can be found as far lateral as lateral tip of the hyoid bone.

Typically, the cyst will move upwards on protrusion of the tongue, given its attachment to the embryonic duct.

Treatment

Treatment for a thyroglossal cyst is called the Sistrunk procedure: surgical resection of the duct to the base of the tongue and removal of the medial segment of the hyoid bone.

Although generally benign the cyst will be removed if the patient exhibits difficulty in breathing or swallowing, or if the cyst is infected. Even if these symptoms are not present the cyst may be removed to eliminate the chance of infection or development of a carcinoma,^[2] or for cosmetic reasons if there is unsightly protrusion from the neck.

The Sistrunk procedure involves excision not only of the cyst but also of the path's tract and branches. A removal of the central portion of the hyoid bone is indicated to ensure complete removal of the tract. It is unlikely that there will be a recurrence after such an operation. The original Sistrunk paper is available on-line with a modern commentary.^[3] At times antibiotics can be indicated if there is sign of infection.

Thyroid scans and thyroid function studies are ordered preoperatively; this is important to demonstrate that normally functioning thyroid tissue is in its usual area.

References

^ SRB's Manual of Surgery 3rd edition 2009;405;406.
^ McNicoll MP, Hawkins DB, England K, Penny R, Maceri DR (1988). "Papillary carcinoma arising in a thyroglossal duct cyst". Otolaryngology-Head and Neck Surgery 99 (1): 50–54. PMID 3140182.
^ "Grand Rounds - Radiology, Respiratory medicine". Retrieved 2010-08-22.

Brewis C, Mahadevan M, Bailey CM, Drake DP (2000). "Investigation and treatment of thyroglossal cysts in children". Journal of the Royal Society of Medicine 93 (1): 18–21. PMC 1288046. PMID 10700841.
http://www.doctoronline.nhs.uk/masterwebsite1Asp/targetpages/testandprocedures/surgery/thyroglo.asp

UpToDate Contents

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1. 甲状舌管嚢胞および異所性甲状腺 thyroglossal duct cysts and ectopic thyroid
2. 頚部腫瘤の鑑別診断 differential diagnosis of a neck mass
3. 嚢胞性甲状腺結節 cystic thyroid nodules
4. 甲状腺の外科解剖学 surgical anatomy of the thyroid gland
5. 小児における先天性および後天性の甲状腺腫 congenital and acquired goiter in children

English Journal

Tall cell carcinoma arising in a thyroglossal duct cyst: A case report.

Gordini L1, Podda F1, Medas F1, Lai ML1, Longheu A1, Pisano G1, Calò PG1.
Annals of medicine and surgery (2012).Ann Med Surg (Lond).2015 Apr 23;4(2):129-32. doi: 10.1016/j.amsu.2015.04.019. eCollection 2015.
INTRODUCTION: Thyroglossal duct cyst carcinomas are extremely rare and their clinical presentation is similar to that of benign cysts. The diagnosis is based on physical examination, laboratory tests, and most importantly multiple imaging techniques (ultrasonography, computed tomography and magnetic
PMID 25973192

Surgical management outcomes of recurrent thyroglossal duct cyst in children - A systematic review.

Ibrahim FF1, Alnoury MK1, Varma N1, Daniel SJ2.
International journal of pediatric otorhinolaryngology.Int J Pediatr Otorhinolaryngol.2015 Jun;79(6):863-7. doi: 10.1016/j.ijporl.2015.03.019. Epub 2015 Mar 28.
OBJECTIVES: Management of recurrent thyroglossal duct cysts (TGDC) remains a clinical challenge to otolaryngologists - head and neck surgeons. The purpose of this systematic review is to determine the best surgical management for recurrent TGDC.METHODS: A comprehensive search for relevant articles w
PMID 25890397

Modified Sistrunk operation: New concept for management of thyroglossal duct cyst.

Ryu YJ1, Kim DW1, Jeon HW1, Chang H1, Sung MW1, Hah JH2.
International journal of pediatric otorhinolaryngology.Int J Pediatr Otorhinolaryngol.2015 Jun;79(6):812-6. doi: 10.1016/j.ijporl.2015.03.001. Epub 2015 Mar 10.
OBJECTIVE: To describe a method of hyoid cartilage division during Sistrunk operation for management of thyroglossal duct cyst (TGDC) and compare postoperative outcomes with those of conventional hyoid bone cutting.METHODS: Fifty-nine patients who received operative treatment for TGDC from January 2
PMID 25829321