Cyst

A cyst /sɪst/ is a closed sac, having a distinct <a href="/facts/Cell_envelope/EHmJsPz3">envelope</a> and <a href="/facts/Cell_division/n5MrunWj">division</a> compared with the nearby <a href="/facts/Biological_tissue/H7CpML7A">tissue</a>. Hence, it is a cluster of <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a> 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 <a href="/facts/Pus/jzNHzM70">pus</a> is called an <a href="/facts/Abscess/BW3TH8kb">abscess</a>, not a cyst. Once formed, a cyst may resolve on its own. When a cyst fails to resolve, it may need to be removed <a href="/facts/Surgically/fG8tWf5Y">surgically</a>, but that would depend upon its type and location.
<a href="/facts/Cancer/PVW6n1D0">Cancer</a>-related cysts are formed as a defense mechanism for the body following the development of <a href="/facts/Mutation/Ee4NnWbY">mutations</a> that lead to an uncontrolled <a href="/facts/Cellular_division/n5MrunWj">cellular division</a>. Once that mutation has occurred, the affected cells divide incessantly and become cancerous, forming a <a href="/facts/Tumor/K0ytzmPz">tumor</a>. 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 <a href="/facts/Blood_vessel/FG3GjPNW">blood vessels</a>, from which they receive nourishment before being contained. Once that happens, the capsule becomes useless, and the tumor may advance from <a href="/facts/Benign_tumor/ssJPkY84">benign</a> to cancerous.
Some cysts are <a href="/facts/Neoplasm/K0ytzmPz">neoplastic</a>, and thus are called cystic tumors. Many types of cysts are not neoplastic, they are <a href="/facts/Dysplasia/sR1UKrbB">dysplastic</a> or <a href="/facts/Metaplasia/k3S1XCrA">metaplastic</a>. <a href="/facts/Pseudocyst/AL75uvex">Pseudocysts</a> are similar to cysts in that they have a sac filled with fluid, but lack an <a href="/facts/Epithelium/ecKHcHC3">epithelial</a> lining.

Cyst open-in-new

Cyst