This article is about cysts in the body. For the ICAO airport code CYST, see St. Theresa Point Airport. For hard-shelled resting stages of some small organisms, see Microbial cyst.
A cyst/sɪst/ is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble); however, the distinguishing aspect of a cyst is that the cells forming the "shell" of such a sac are distinctly abnormal (in both appearance and behaviour) when compared with all surrounding cells for that given location. A cyst may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst may resolve on its own. When a cyst fails to resolve, it may need to be removed surgically, but that would depend upon its type and location.
Cancer-related cysts are formed as a defense mechanism for the body following the development of mutations that lead to an uncontrolled cellular division. Once that mutation has occurred, the affected cells divide incessantly and become cancerous, forming a tumor. The body encapsulates those cells to try to prevent them from continuing their division and contain the tumor, which becomes known as a cyst. That said, the cancerous cells still may mutate further and gain the ability to form their own blood vessels, from which they receive nourishment before being contained. Once that happens, the capsule becomes useless, and the tumor may advance from benign to cancerous.
Some cysts are neoplastic, and thus are called cystic tumors. Many types of cysts are not neoplastic, they are dysplastic or metaplastic. Pseudocysts are similar to cysts in that they have a sac filled with fluid, but lack an epithelial lining.
Terminology
microcyst – a small cyst that requires magnification to be seen
macrocyst – a cyst that is larger than usual or compared to others
Related structures
A pseudocyst is very similar to a cyst, but is a collection of cells without a distinct membrane (epithelial or endothelial cells).
Adrenal cyst (glands located above the kidneys) - It is a rare disease, affecting 0.06 to 0.18% of autopsy studies. It constitutes 5.4 to 6.0% of adrenal gland diseases. There are five major types of adrenal cysts: simple or endothelial cysts, true or epithelial cysts, pseudocysts, parasitic cysts, and cysts not classified elsewhere. 7% of the cysts can be malignant.[9]
Peritoneal inclusion cyst (lining of the abdominal cavity) - It is a cluster of fluid-filled cysts lining the abdominal cavity of reproductive age women with a history of pelvic, abdominal surgeries, or abdominal inflammation. Those affected maybe presented with an abdominal, pelvic, lower back that lasted for months.[11]
This is just one example of how the Greek root cyst-, which simply means a fluid-filled sac, also is found in medical terms that relate to the urinary bladder and the gallbladder, neither of which involve cysts.
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^Zadik Y, Aktaş A, Drucker S, Nitzan DW (December 2012). "Aneurysmal bone cyst of mandibular condyle: a case report and review of the literature". Journal of Cranio-Maxillo-Facial Surgery. 40 (8): e243-8. doi:10.1016/j.jcms.2011.10.026. PMID22118925.
^Bancroft LW, Peterson JJ, Kransdorf MJ (January 2004). "Cysts, geodes, and erosions". Radiologic Clinics of North America. 42 (1): 73–87. doi:10.1016/S0033-8389(03)00165-9. PMID15049524.
^Zadik Y, Yitschaky O, Neuman T, Nitzan DW (July 2011). "On the self-resolution nature of the buccal bifurcation cyst". Journal of Oral and Maxillofacial Surgery. 69 (7): e282-4. doi:10.1016/j.joms.2011.02.124. PMID21571416.
