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The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thyroid is located at the front of the neck, below the Adam's apple. Microscopically, the functional unit of the thyroid gland is the spherical thyroid follicle, lined with follicular cells (thyrocytes), and occasional parafollicular cells that surround a lumen containing colloid. The thyroid gland secretes three hormones: the two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – and a peptide hormone, calcitonin. The thyroid hormones influence the metabolic rate and protein synthesis, and in children, growth and development. Calcitonin plays a role in calcium homeostasis. Secretion of the two thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary gland. TSH is regulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus.
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 specifically to 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.
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. There are also two other types of salivary glands; they are submandibular and sublingual glands. Sometimes accessory parotid glands are found close to the main parotid glands.
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 develops from cells and tissues left over after the formation of the thyroid gland during developmental stages.
Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin, hollow needle is inserted into the mass for sampling of cells that, after being stained, are examined under a microscope (biopsy). The sampling and biopsy considered together are called fine-needle aspiration biopsy (FNAB) or fine-needle aspiration cytology (FNAC). Fine-needle aspiration biopsies are very safe minor surgical procedures. Often, a major surgical biopsy can be avoided by performing a needle aspiration biopsy instead, eliminating the need for hospitalization. In 1981, the first fine-needle aspiration biopsy in the United States was done at Maimonides Medical Center. Today, this procedure is widely used in the diagnosis of cancer and inflammatory conditions.
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.
Pleomorphic adenoma is a common benign salivary gland neoplasm characterised by neoplastic proliferation of parenchymatous glandular cells along with myoepithelial components, having a malignant potentiality. It is the most common type of salivary gland tumor and the most common tumor of the parotid gland. It derives its name from the architectural Pleomorphism seen by light microscopy. It is also known as "Mixed tumor, salivary gland type", which refers to its dual origin from epithelial and myoepithelial elements as opposed to its pleomorphic appearance.
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 neurogenic tumors, usually found in the posterior mediastinum, followed by thymoma (15–20%) located in the anterior mediastinum. Lung cancer typically spreads to the lymph nodes in the mediastinum.
Papillary thyroid cancer or papillary thyroid carcinoma 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.
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 times more common in adults than in fetuses. Because of the variations and rarity, it may lead to surgical complications.
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.
A branchial cleft 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.
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.
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.
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.
A breast mass, also known as a breast lump, is a localized swelling that feel 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.
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 under ultrasound, MRI or a stereotactic biopsy technique. 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.
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 the 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. 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 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.
- 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.
- 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.
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- ↑ 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.
- 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.
- ↑ 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.
- ↑ 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.
- 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.
- 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.
- ↑ 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.
- ↑ 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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