Cyst


A cyst is a closed sac, having a distinct envelop and division compared with the nearby tissue. Hence, it is a cluster of cells that has grouped together to form a sac ; however, the distinguishing aspect of a cyst is that the cells forming the "shell" of such a sac are distinctly abnormal when compared with all surrounding cells for that given location. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, sometimes 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, forming a tumour. The body encapsulates those cells to try to prevent them from continuing their division and to try to contain the tumour, 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 tumour may advance from benign to a cancer.
Some cysts are neoplastic and thus, are called cystic tumors; many types are not neoplastic. Some are dysplastic or metaplastic. Pseudocysts are similar to cysts, but lack an epithelial lining.

Terminology

A small cyst that requires magnification to be seen, may be called a microcyst. Similarly, a cyst that is larger than usual or compared to others, may be called a macrocyst.

Types

By location

Female reproductive system

Cutaneous (skin) and [subcutaneous] cysts

[Popliteal fossa]

Head and neck

Chest

Kidneys and adrenal glands

Brain

[Scrotum]

Liver cyst

Fingers

[Bone cyst]

Others

Cysts commonly seen in various locations

Despite being described in 1938 as the microscopic appearance of cysts in the pancreas, cystic fibrosis is an example of a genetic disorder whose name is related to fibrosis of the cystic duct and does not involve cysts.
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.

Cystic neoplasm

Examples of neoplastic cysts include:
Treatment ranges from simple enucleation of the cyst to curettage to resection. There are cysts—e.g., buccal bifurcation cyst—that resolve on their own, in which just close observation may be employed, unless it is infected and symptomatic.

Related structures

A pseudocyst is similar collection without a distinct membrane.
A syrinx in the spinal cord or brainstem is sometimes inaccurately referred to as a cyst.