|Classification and external resources|
A thyroglossal cyst is a fibrous cyst that forms from a persistent thyroglossal duct. Thyroglossal cysts can be defined as an irregular neck mass or a lump which had developed from cells and tissues left over after the formation of the thyroid gland during developmental stages.
Thyroglossal cysts are the most common cause of midline neck masses and are generally located substandard to the hyoid bone, yet these neck masses can occur anywhere along the path of the thyroid gland from the base of the tongue to the suprasternal notch.
Other common causes of midline neck masses include lymphadenopathy, dermoid cysts, and various odontogenic anomalies.
Thyroglossal cyst are developed at birth and can have many diagnostic procedures to establish the degree of the cyst. Also complications can come along with the before and after masses of the Thyroglossal Cysts, treatments are available to help with pain and reduction of the cyst.
It usually presents as a midline neck lump (in the region of the hyoid bone) that is usually painless, smooth and cystic, though if infected, pain can occur. There may be difficulty breathing, dysphagia (difficulty swallowing), or dyspepsia (discomfort in the upper abdomen), especially if the lump becomes large.
The most common location 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 Duct Cysts are developed as a birth defect. During the embryonic development the thyroid gland is being formed beginning at the base of the tongue moving towards the neck canal, known as the thyroglossal duct. Once the thyroid reaches its final position in the neck the duct normally disappears. Yet, in some cases portions of the duct remain behind leaving small pockets, known as cysts. During a person's life these cyst pockets can fill with fluids and mucus, enlarging when infected, presenting the thyroglossal cyst.
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.
The diagnosis of a thyroglossal duct cyst needs to be examined by medical professions and is usually done by a physical exam. It is important to identify whether or not the thyroglossal cyst contains any thyroid tissue as it can define the degree of cyst that is being dealt with.
Diagnosis procedures for a thyroglossal cyst include:
|Blood Tests||Blood tests generally aim to test the thyroid function.|
|Ultrasounds||Ultrasounds use high frequency sound waves to create images of blood vessels, tissues and organs through a computer to examine the degree of mass and its surrounding tissues.|
|Thyroid Scans||Radioactive iodine or technetium (a radioactive metallic element) is used in this procedure to show any abnormalities of the thyroid.|
|Fine Needle Aspiration||The removal of cells from the cyst using a needle to diagnose correctly.|
Thyroglossal duct cysts most often present with a palpable 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 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, as well as on swallowing because of attachment of the tract to the foramen caecum.
An infected thyroglossal duct cyst can occur when it is left untreated for a certain amount of time or simply when a thyroglossal duct cyst hasn't been suspected by a person. The degree of infection can be examined as major rim enhancement has occurred, located inferior to the hyoid bone. Also soft tissue swelling occurs along with airway obstruction and trouble swallowing due to the rapid enlargement of the cyst.
With infections there can be rare cases where an expression of fluid is projected into the pharynx causing other problems within the neck. Infections can occur before and after the removal of the thyrglossal duct cyst. The infections that occur after the removal of the cyst include skin reactions, including shiny skin, redness and dryness from stitching and the healing process of the skin being exposed to other bacteria.
With a Thyroglossal duct cysts ruptures can occur unexpectedly, resulting draining sinuses known as thyroglossal fistula. Thyroglossal fistula can develop when the removal of the cyst has not been fully completed. This is usually noticed when bleeding in the neck occurs causing swelling and fluid ejection around the original wound of removal. Breathing and swallowing problems can also be of occurrence due to pressure within the neck.
Thyroglossal duct cyst carcinoma
In rare cases of thyroglossal cysts cancer can be presented. It is a very uncommon and the management for it can be seen as controversial. When thyroglossal carcinoma occurs they are presented with a tumor, which usually arise's from the ectopic thyroid tissue within the cyst. This can result in the surgical removal of the lymph nodes and thyroid gland to stop any spreading of cancer to the rest of the body.
Treatment for a thyroglossal cyst is called the Sistrunk procedure: surgical resection of the duct to the base of the trunk and removal of the central portion 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, 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. At times antibiotics can be administered 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.
- 90% of cases are presented in children before the age of 10 
- 70% of neck anomalies are from Thyroglossal cysts 
- Thyroglossal Duct Cysts are the second most common neck abnormalities after lymphadenopathy
- A person can live with a Thyroglossal Duct Cyst without any problems, until an infection is presented
- Approximately 7% of the population has thyroglossal duct remnants 
- Thyroglossal duct carcinoma occurs in approximately 1 to 2% of Thyroglossal cyst cases.
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