Ectopic thymus

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Ectopic thymus
Specialty Otorhinolaryngology
Symptoms neck mass, sometimes hoarse voice, stridor, shortness of breath, dysphagia
Causesembryological defect of movement of thymus tissue
Diagnostic method ultrasound, magnetic resonance imaging
Differential diagnosis thyroglossal cyst, branchial cleft cyst, dermoid cyst, lymphadenitis, tumours
Treatment surgery if symptoms, watch and wait if no symptoms
Prognosis good
Frequencyunknown

Ectopic thymus is a condition where thymus tissue is found in an abnormal location (ectopia). It usually does not cause symptoms, but may leads to a mass in the neck that may compress the trachea and the esophagus. It is thought to be the result of either a failure of descent or a failure of involution of normal thymus tissue. It may be diagnosed with radiology, such as an ultrasound or magnetic resonance imaging. If it causes illness, surgery can be used to remove it. Recurrence after surgery is very unlikely.

Contents

Signs and symptoms

Ectopic thymus most often does not cause symptoms. [1] It is most frequently discovered as a soft mass or swelling in the neck of infants and children. [2] However, when symptoms do occur they are most commonly due to compression of nearby structures such as the trachea and esophagus. This can lead to hoarse voice, stridor, difficulty breathing and/or difficulty swallowing. [3] [4] Pain is uncommon. [5]

Cause

During embryological development, the thymus is formed from the third and fourth pharyngeal pouches. [1] It descends along a pathway from the mandible to its final resting place of the mediastinum. [2] When the thymus tissue fails to descend appropriately or fails to involute, thymus tissue remains in various locations along this pathway. Locations that solid thymus tissue has been reported include near the thyroid (most common), within the thyroid, the base of the skull, and within the pharynx or trachea. [6] [2]

Diagnosis

Ultrasound is the recommended diagnostic modality used to diagnose cervical ectopic thymus. [6] The thymus has a unique appearance on ultrasound, which allows for specific diagnosis. [7] [8] Ectopic thymus appears hypoechoic, with characteristic linear echogenic foci. [3] Magnetic resonance imaging may be utilized as well to better characterize and identify the location of the ectopic thymus. [2] On MRI, ectopic cervical thymus appears as a homogeneous mass which is isointense to muscle on T1-weighted scans and hyperintense on T2-weighted scans. [3] Biopsy or histological examination upon resection can also be used to make a definitive diagnosis. [6] [9] Sometimes, ectopic thymus is found incidentally during neck surgery. [6]

Differential diagnosis

An appropriate differential diagnosis depends upon location of the ectopic thymus. For cervical ectopic thymus, the differential diagnosis should include additional causes of neck masses. This includes common causes of neck masses in children, including:

Rare causes of neck masses in children include:

Treatment

If the patient is asymptomatic and the mass is identified based upon radiologic findings, biopsy and/or resection may be avoided. [6] [9] Surgical removal of the mass is the definitive treatment for ectopic thymus tissue that is causing symptoms. [4] It has been reported that the ectopic thymus tissue can transform into cancerous tissue. [4] However, due to most diagnosed ectopic thymus tissue being resected due to this concern, the natural progression is not well explored. The data supporting malignant transformation is limited, and ectopic thymus tissue that is not causing problems can likely be left to involute. [11] Given the thymus's role in the body's adaptive immune system, it should be confirmed that the patient has a mediastinal thymus prior to surgery in order to prevent the potential for future immunodeficiencies. [4]

Prognosis

Following surgical removal of the ectopic thymus, there have been no reported recurrences. [4]

Epidemiology

Because ectopic thymus usually does not cause symptoms, it is hard to determine prevalence. [1] Ectopic thymus is rarely reported in the literature. [2] The prevalence of ectopic thymus reportedly ranges from 1 to 90%. This variation in prevalence is largely dependent upon the method of investigation used and how extensive the workup is. [12] With most ectopic thymus tissue being asymptomatic, it is likely the prevalence is higher than typically reported. [3]

Related Research Articles

<span class="mw-page-title-main">Thymus</span> Endocrine gland

The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule.

<span class="mw-page-title-main">Brachiocephalic artery</span> Artery of the mediastinum

The brachiocephalic artery, brachiocephalic trunk, or innominate artery is an artery of the mediastinum that supplies blood to the right arm, head, and neck.

<span class="mw-page-title-main">Thyroglossal cyst</span> Medical condition

A thyroglossal cyst or thyroglossal duct 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 develops from cells and tissues left over after the formation of the thyroid gland during developmental stages.

<span class="mw-page-title-main">Pancoast tumor</span> Medical condition

A Pancoast tumor is a tumor of the apex of the lung. It is a type of lung cancer defined primarily by its location situated at the top end of either the right or left lung. It typically spreads to nearby tissues such as the ribs and vertebrae. Most Pancoast tumors are non-small-cell lung cancers.

<span class="mw-page-title-main">Thyroid disease</span> Medical condition

Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ. These hormones normally act in the body to regulate energy use, infant development, and childhood development.

<span class="mw-page-title-main">Mediastinal tumors</span> Medical condition

A mediastinal tumor is a tumor in the mediastinum, the cavity that separates the lungs from the rest of the chest. It contains the heart, esophagus, trachea, thymus, and aorta. The most common mediastinal masses are thymoma, usually found in the anterior mediastinum, followed by neurogenic Timor (15–20%) located in the anterior mediastinum. Lung cancer typically spreads to the lymph nodes in the mediastinum.

<span class="mw-page-title-main">Papillary thyroid cancer</span> Medical condition

Papillary thyroid cancer is the most common type of thyroid cancer, representing 75 percent to 85 percent of all thyroid cancer cases. It occurs more frequently in women and presents in the 20–55 year age group. It is also the predominant cancer type in children with thyroid cancer, and in patients with thyroid cancer who have had previous radiation to the head and neck. It is often well-differentiated, slow-growing, and localized, although it can metastasize.

<span class="mw-page-title-main">Thyroid ima artery</span> Artery of the head and neck

The thyroid ima artery is an artery of the head and neck. It is an anatomical variant that, when present, supplies blood to the thyroid gland primarily, or the trachea, the parathyroid gland and the thymus gland in rare cases. It has also been reported to be a compensatory artery when one or both of the inferior thyroid arteries are absent, and in a few cases the only source of blood to the thyroid gland. Furthermore, it varies in origin, size, blood supply, and termination, and occurs in around 3.8% of the population and is 4.5 times more common in fetuses than in adults. Because of the variations and rarity, it may lead to surgical complications, particularly during tracheostomy and other airway managements.

<span class="mw-page-title-main">Stafne defect</span> Mandibular depression

The Stafne defect is a depression of the mandible, most commonly located on the lingual surface. The Stafne defect is thought to be a normal anatomical variant, as the depression is created by ectopic salivary gland tissue associated with the submandibular gland and does not represent a pathologic lesion as such. This cavity is commonly observed on panoramic radiograph.

<span class="mw-page-title-main">Persistent thyroglossal duct</span> Medical condition

A persistent thyroglossal duct is a usually benign medical condition in which the thyroglossal duct, a structure usually only found during embryonic development, fails to atrophy. The duct persists as a midline structure forming an open connection between the back of the tongue and the thyroid gland. This opening can lead to fluid accumulation and infection, which necessitate the removal of the duct.

<span class="mw-page-title-main">Branchial cleft cyst</span> Medical condition

A branchial cleft cyst or simply branchial cyst is a cyst as a swelling in the upper part of neck anterior to sternocleidomastoid. It can, but does not necessarily, have an opening to the skin surface, called a fistula. The cause is usually a developmental abnormality arising in the early prenatal period, typically failure of obliteration of the second, third, and fourth branchial cleft, i.e. failure of fusion of the second branchial arches and epicardial ridge in lower part of the neck. Branchial cleft cysts account for almost 20% of neck masses in children. Less commonly, the cysts can develop from the first, third, or fourth clefts, and their location and the location of associated fistulas differs accordingly.

<span class="mw-page-title-main">Thyroid nodule</span> Lump of tissue or fluid in the thyroid gland

Thyroid nodules are nodules which commonly arise within an otherwise normal thyroid gland. They may be hyperplastic or tumorous, but only a small percentage of thyroid tumors are malignant. Small, asymptomatic nodules are common, and often go unnoticed. Nodules that grow larger or produce symptoms may eventually need medical care. A goitre may have one nodule – uninodular, multiple nodules – multinodular, or be diffuse.

<span class="mw-page-title-main">Parathyroid adenoma</span> Medical condition

A parathyroid adenoma is a benign tumor of the parathyroid gland. It generally causes hyperparathyroidism; there are very few reports of parathyroid adenomas that were not associated with hyperparathyroidism.

<span class="mw-page-title-main">Parathyroid disease</span> Medical condition

Many conditions are associated with disorders of the function of the parathyroid gland. Some disorders may be purely anatomical resulting in an enlarged gland which will raise concern. Such benign disorders, such as parathyroid cyst, are not discussed here. Parathyroid diseases can be divided into those causing hyperparathyroidism, and those causing hypoparathyroidism.

<span class="mw-page-title-main">Breast mass</span> Localized swellings that feel different from the surrounding tissue

A breast mass, also known as a breast lump, is a localized swelling that feels different from the surrounding tissue. Breast pain, nipple discharge, or skin changes may be present. Concerning findings include masses that are hard, do not move easily, are of an irregular shape, or are firmly attached to surrounding tissue.

Theca lutein cyst is a type of bilateral functional ovarian cyst filled with clear, straw-colored fluid. These cysts result from exaggerated physiological stimulation due to elevated levels of beta-human chorionic gonadotropin (beta-hCG) or hypersensitivity to beta-hCG. On ultrasound and MRI, theca lutein cysts appear in multiples on ovaries that are enlarged.

<span class="mw-page-title-main">Breast biopsy</span> Surgical diagnostic procedure for breast tumours

A breast biopsy is usually done after a suspicious lesion is discovered on either mammography or ultrasound to get tissue for pathological diagnosis. Several methods for a breast biopsy now exist. The most appropriate method of biopsy for a patient depends upon a variety of factors, including the size, location, appearance and characteristics of the abnormality. The different types of breast biopsies include fine-needle aspiration (FNA), vacuum-assisted biopsy, core needle biopsy, and surgical excision biopsy. Breast biopsies can be done utilizing ultrasound, MRI or a stereotactic biopsy imaging guidance. Vacuum assisted biopsies are typically done using stereotactic techniques when the suspicious lesion can only be seen on mammography. On average, 5–10 biopsies of a suspicious breast lesion will lead to the diagnosis of one case of breast cancer. Needle biopsies have largely replaced open surgical biopsies in the initial assessment of imaging as well as palpable abnormalities in the breast.

<span class="mw-page-title-main">Vaginal cysts</span> Benign growths of the vaginal epithelium

Vaginal cysts are uncommon benign cysts that develop in the vaginal wall. The type of epithelial tissue lining a cyst is used to classify these growths. They can be congenital. They can present in childhood and adulthood. The most common type is the squamous inclusion cyst. It develops within vaginal tissue present at the site of an episiotomy or other vaginal surgical sites. In most instances they do not cause symptoms and present with few or no complications. A vaginal cyst can develop on the surface of the vaginal epithelium or in deeper layers. Often, they are found by the woman herself and as an incidental finding during a routine pelvic examination. Vaginal cysts can mimic other structures that protrude from the vagina such as a rectocele and cystocele. Some cysts can be distinguished visually but most will need a biopsy to determine the type. Vaginal cysts can vary in size and can grow as large as 7 cm. Other cysts can be present on the vaginal wall though mostly these can be differentiated. Vaginal cysts can often be palpated (felt) by a clinician. Vaginal cysts are one type of vaginal mass, others include cancers and tumors. The prevalence of vaginal cysts is uncertain since many go unreported but it is estimated that 1 out of 200 women have a vaginal cyst. Vaginal cysts may initially be discovered during pregnancy and childbirth. These are then treated to provide an unobstructed delivery of the infant. Growths that originate from the urethra and other tissue can present as cysts of the vagina.

In CT scan of the thyroid, focal and diffuse thyroid abnormalities are commonly encountered. These findings can often lead to a diagnostic dilemma, as the CT reflects nonspecific appearances. Ultrasound (US) examination has a superior spatial resolution and is considered the modality of choice for thyroid evaluation. Nevertheless, CT detects incidental thyroid nodules (ITNs) and plays an important role in the evaluation of thyroid cancer.

A cervical thymic cyst, also called thymopharyngeal duct cyst, is a fluid-filled mass that occurs when the thymopharyngeal duct, an embryonic structure connecting the nascent thymus with the embryonic pharynx, fails to close and disappear. A thymic cyst is typically a solitary mass on one side of the neck, and is usually found near the carotid sheath. Some cervical thymic cysts may extend into the mediastinum. It is usually asymptomatic. The diagnostic process includes differentiating between other causes of neck masses in infants and children, including branchial cleft cysts and cystic hygromas. The treatment is surgical excision. On histologic examination, the wall of the cyst includes thymic tissue, and may include parathyroid gland tissue because of the parathyroid gland's common embryonic origin with the thymus gland in the third pharyngeal pouch. Fewer than 100 cases of cervical thymic cysts have been reported in the medical literature.

References

  1. 1 2 3 Grevellec, Armelle; Tucker, Abigail S. (2010-05-01). "The pharyngeal pouches and clefts: Development, evolution, structure and derivatives". Seminars in Cell & Developmental Biology. Molecular Motors in Mitosis. 21 (3): 325–332. doi:10.1016/j.semcdb.2010.01.022. ISSN   1084-9521. PMID   20144910.
  2. 1 2 3 4 5 Lavini, Corrado; Moran, Cesar A.; Morandi, Uliano; Schoenhuber, Rudolf (2009-05-08). Thymus Gland Pathology: Clinical, Diagnostic and Therapeutic Features. Springer Science & Business Media. ISBN   978-88-470-0828-1.
  3. 1 2 3 4 Herman, T. E.; Siegel, M. J. (February 2009). "Cervical ectopic thymus". Journal of Perinatology. 29 (2): 173–174. doi: 10.1038/jp.2008.89 . ISSN   1476-5543. PMID   19177048.
  4. 1 2 3 4 5 Anastasiadis, Kyriakos; Ratnatunga, Chandi (2007-06-07). The Thymus Gland: Diagnosis and Surgical Management. Springer Science & Business Media. ISBN   978-3-540-33426-2.
  5. ↑ De Foer, B.; Vercruysse, J. Ph.; Mariën, P.; Colpaert, C.; Pilet, B.; Pouillon, M.; Smet, M. H.; Casselman, J. W.; Breysem, L. (2007). "Cervical ectopic thymus presenting as a painless neck mass in a child". Journal of the Belgian Society of Radiology. 90: 281–283.
  6. 1 2 3 4 5 6 7 8 Bang, Myung Hoon; Shin, JinShik; Lee, Kwan Seop; Kang, Min Jae (2018-04-06). "Intrathyroidal ectopic thymus in children". Medicine. 97 (14): e0282. doi:10.1097/MD.0000000000010282. ISSN   0025-7974. PMC   5902273 . PMID   29620644.
  7. ↑ Han, Bokyung K.; Yoon, H.-K.; Suh, Yeon-Lim (2001-07-01). "Thymic ultrasound". Pediatric Radiology. 31 (7): 480–487. doi:10.1007/s002470100468. ISSN   1432-1998. PMID   11486800. S2CID   2797344.
  8. ↑ Yildiz, Adalet Elcin; Ceyhan, Koray; Sıklar, Zeynep; Bilir, Pelin; Yağmurlu, Emin Aydın; Berberoğlu, Merih; Fitoz, Suat (September 2015). "Intrathyroidal Ectopic Thymus in Children: Retrospective Analysis of Grayscale and Doppler Sonographic Features". Journal of Ultrasound in Medicine. 34 (9): 1651–1656. doi:10.7863/ultra.15.14.10041. ISSN   1550-9613. PMID   26269296. S2CID   31698111.
  9. 1 2 Zielke, Anna M.; Swischuk, Leonard E.; Hernandez, J. Alberto (2007-11-01). "Ectopic cervical thymic tissue: can imaging obviate biopsy and surgical removal?". Pediatric Radiology. 37 (11): 1174–1177. doi:10.1007/s00247-007-0598-7. ISSN   1432-1998. PMID   17851657. S2CID   22161921.
  10. 1 2 3 4 5 6 7 8 9 10 11 Philadelphia, The Children's Hospital of (2016-04-11). "Neck Masses". www.chop.edu. Retrieved 2020-04-11.
  11. ↑ Schloegel, Luke J.; Gottschall, Joshua A. (2009-03-01). "Ectopic cervical thymus: Is empiric surgical excision necessary?". International Journal of Pediatric Otorhinolaryngology. 73 (3): 475–479. doi:10.1016/j.ijporl.2008.10.031. ISSN   0165-5876. PMID   19117616.
  12. ↑ Marx, A.; Rüdiger, T.; Rößner, E.; Tzankov, A.; de Montpréville, V. T.; Rieker, R. R.; Ströbel, P.; Weis, C.‑A. (2018-09-01). "Ektopien des Thymus und ektope Thymustumoren". Der Pathologe (in German). 39 (5): 390–397. doi:10.1007/s00292-018-0485-z. ISSN   1432-1963. PMID   30159601. S2CID   52123197.
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