Cyst

A cyst is a closed sac, having a distinct membrane and division compared to the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.

Types

 * Acne cyst – Pseudocysts associated with cystic acne. Actually an inflammatory nodule with or without an associated epidermoid inclusion cyst.
 * Aneurysmal bone cyst (Aggressive lesion with radiographic cystic appearance)
 * Arachnoid cyst (between the surface of the brain and the cranial base or on the arachnoid membrane)
 * Baker's cyst or popliteal cyst (behind the knee joint)
 * Bartholin's cyst
 * Breast cyst
 * Buccal bifurcation cyst
 * Calcifying odontogenic cyst
 * Chalazion cyst (eyelid)
 * Chocolate cyst
 * Choroid plexus cyst (brain)
 * Colloid cyst
 * Cysticercal cyst (the larval stage of Taenia sp. (Crain's backs))
 * Dentigerous cyst (associated with the crowns of non-erupted teeth)
 * Dermoid cyst (ovaries, testes, many other locations from head to tailbone)
 * Epididymal cyst (found in the vessels attached to the testes)
 * Ganglion cyst (hand/foot joints and tendons)
 * Glandular odontogenic cyst
 * Glial cyst (in the brain)
 * Gartner's duct cyst (vaginal or vulvar cyst of embryological origin)
 * Hydatid cyst (larval stage of Echinococcus granulosus (tapeworm))
 * Hydrocele (testicle)
 * Keratocyst (in the jaws, these can appear solitary or associated with the Gorlin-Goltz or Nevoid basal cell carcinoma syndrome. The latest World Health Organization classification considers Keratocysts as tumors rather than cysts)
 * Liver cystic disease
 * Meibomian cyst (eyelid)
 * Mucoid cyst (ganglion cysts of the digits)
 * Mucous cyst of the oral mucosa
 * Nabothian cyst (cervix)
 * Nasolabial duct cyst
 * Odontogenic cyst (teeth)
 * Ovarian cyst (ovaries, functional and pathological)
 * Pancreatic cyst
 * Paradental cyst
 * Parapelvic cyst (kidney)
 * Paratubal cyst (fallopian tube)
 * Periapical cyst (This cyst, also known as radicular cyst, is the most common odontogenic cyst)
 * Pericardial cyst
 * Peritoneal cyst (lining of the abdominal cavity)
 * Pilar cyst (cyst of the scalp)
 * Pilonidal cyst (skin infection near tailbone)
 * Renal cyst (kidneys)
 * Polycystic ovary syndrome
 * Pineal gland cyst
 * Radicular cyst (associated with the roots of non-vital teeth, also known as periapical cyst)
 * Residual cyst
 * Sebaceous cyst (sac below skin)
 * Spermatocele (testicle)
 * Stafne static bone cyst (An anatomic variant with radiographic cystic appearance in the posterior mandible)
 * Tarlov cyst (spine)
 * Trichilemmal cyst – Same as a pilar cyst. A familial cyst of the scalp.
 * Vocal fold cyst

Cystic fibrosis
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 actual cysts.

Cystic neoplasm
Most cysts in the body are benign (dysfunctional) tumors, the result of plugged ducts or other natural body outlets for secretions. However sometimes these masses are considered neoplasm:
 * Dermoid cyst
 * Keratocystic odontogenic tumor
 * Calcifying odontogenic cyst

Treatment
Treatment ranges from simple enucleation of the cyst to curettage to resection. There are cysts, e.g. buccal bifurcation cyst with self-resolation nature, in which close observation only can be employed unless the cyst is infected and symptomatic.

Related structures
A pseudocyst is collection without a distinct membrane.

A syrinx in the spinal cord or brainstem is sometimes inaccurately referred to as a cyst.