Cysts are closed capsule or sac-like structures, typically filled with liquid, semisolid, or gaseous material, very much like a blister. In this article we will describe the various types. Cysts occur within tissue and can affect any part of the body. They vary in size from microscopic to the size of some team-sport balls – large cysts can displace internal organs.
In anatomy, a cyst can also refer to any normal bag or sac in the body, such as the bladder. In this article, cyst refers to an abnormal sac or pocket in the body that contains liquid, gaseous, or semisolid substances.
A cyst is not a normal part of the tissue where it is located. It has a distinct membrane and is separated from nearby tissue – the outer (capsular) portion of a cyst is called the cyst wall. If the sac is filled with pus it is not a cyst; it is an abscess.
Most cysts are benign and are caused by blockages in the body’s natural drainage systems. However, some cysts may be tumors that form inside tumors – these can potentially be malignant. Examples include keratocysts and dermoid cysts.
Signs and symptoms vary enormously depending on what type of cyst it is. In many cases, a person becomes aware of an abnormal lump, particularly in cases with cysts of the skin or when a cyst is just below the skin. A person may notice a cyst in their breasts when they examine them by touching them. Breast cysts are often painful.