A cyst is a closed sac, having a distinct membrane and division compared to the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (not unlike the manner in which water molecules group together, forming 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 behavior) when compared to all surrounding cells to 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, a cyst may sometimes resolve on its own. When a cyst fails to resolve it may need to be removed by surgery surgery, but this will depend on what type of cystitis and where in the body it has formed.
Some cysts are neoplastic and are thus called cystic tumors; many types are not neoplastic. Some are dysplastic or metaplastic. Pseudocysts are similar to cysts (having a sac filled with fluid) but lack an epithelial lining.
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 (which serves the gallbladder) and does not involve actual cysts.This is just one example of how the Greek root cyst-, which simply means a fluid-filled sac, is also found in medical terms that relate to the urinary bladder and the gallbladder but that have nothing to do with cysts.