A cyst is a closed sac or pouch that has a distinct membrane that separates it from surrounding tissue and contains air, fluid, semifluid or solid material. It is usually created by developmental anomalies, obstruction of ducts or parasitic infection.
There are many types of cysts including, but not limited to:
- congenital cysts, which are present at birth and are the result of abnormal developments such as the imperfect closure of spina bifida
- daughter cysts, which are cysts growing out of other cysts
- dermoid cysts, which are either ovarian teratomas or nonmalignant cystic tumors containing elements such as hair, teeth or skin
- epidermoid cysts, which contain skin debris and commonly form on the scalp, the back of the neck or the maxilla
- parasitic cysts, which enclose the larval forms of some parasites
- retention cysts, which retain the secretions of glands