What is the definition or description of: cyst?

Looks bad but not!: A cyst is a closed sac having a distinct membrane and developing abnormally in a body cavity or structure . Generally benign, there are very few diagnosis that alarm patients that they may have a tumor. Always discuss with your doctor but generally a harmless sac like growth. The classic cyst on the hand is a ganglion cyst.

Lined sac: A cyst is a structure or mass that consists of a cellular lined sac. It is typically filled with fluid but may be filled with solid material. It can be congenital, traumatic, or acquired. They may develop nearly anywhere in the body and usually require complete excision for eradication or they are likely to recur. Fluid filled sacs that are not cellular lined may be called pseudo-cysts.