A cyst is a closed sac, having a distinct membrane

Biological membrane

A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

 and division

Cell division

Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

 on the nearby tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

. It may contain air, fluids, or semi-solid material. A collection of pus

Pus

Pus is a viscous exudate, typically whitish-yellow, yellow, or yellow-brown, formed at the site of inflammatory during infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection of pus within or beneath the epidermis is known as a pustule or...

 is called an abscess

Abscess

An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.

Locations

• Acne
  Acne
  Acne is a general term used for acneiform eruptions. It is usually used as a synonym for acne vulgaris, but may also refer to:*Acne aestivalis*Acne conglobata*Acne cosmetica*Acne fulminans*Acne keloidalis nuchae*Acne mechanica...
  
   cyst – Pseudocysts associated with cystic acne. Actually an inflammatory nodule with or without an associated epidermoid inclusion cyst.
• Arachnoid cyst
  Arachnoid cyst
  Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells and collagen that may develop between the surface of the brain and the cranial base or on the arachnoid membrane, one of the three membranes that cover the brain and the spinal cord...
  
   (between the surface of the brain and the cranial base or on the arachnoid membrane)
• Baker's cyst
  Baker's cyst
  A Baker's cyst, also known as a popliteal cyst, is a benign swelling of the semimembranous or more rarely some other synovial bursa found behind the knee joint. It is named after the surgeon who first described it, William Morrant Baker...
  
   or popliteal cyst (behind the knee joint)
• Bartholin's cyst
  Bartholin's cyst
  A Bartholin's cyst is formed when a Bartholin's gland is blocked, causing a fluid-filled cyst to develop. A Bartholin's cyst is not an infection, although it can be caused by an infection, inflammation, or physical blockage to the Bartholin's ducts . If infection sets in, the result is a...
  
  
• Breast cyst
  Breast cyst
  A breast cyst is a fluid-filled sac within the breast. One can have one or more breast cysts. They're often described as round or oval lumps with distinct edges. In texture, a breast cyst usually feels like a soft grape or a water-filled balloon, but sometimes a breast cyst feels firm.Breast cysts...
  
  
• Buccal bifurcation cyst
  Buccal bifurcation cyst
  Buccal bifurcation cyst is an inflammatory odontogenic cyst, of the paradental cysts family, that typically appears in the buccal bifurcation region of the mandibular first molars in the second half of the first decade of life...
  
  
• Calcifying odontogenic cyst
  Calcifying odontogenic cyst
  The calcifying odotogenic cyst, also known as the Gorlin cyst, is a cyst most likely to affect the anterior areas of the jaws. It is most common in people in their second to third decades but can be seen at almost any age. On radiographs, the calcifying odontogenic cyst appears as a unilocular...
  
  
• Chalazion cyst
  Chalazion
  A chalazion , also known as a meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of a blocked meibomian gland, usually on the upper eyelid. Chalazia differ from styes in that they are subacute and usually painless nodules...
  
   (eyelid)
• Choroid plexus cyst
  Choroid plexus cyst
  Choroid plexus cysts are cysts that occur within choroid plexus of the brain. The brain contains pockets or spaces called ventricles with a spongy layer of cells and blood vessels called the choroid plexus. This is in the middle of the fetal brain. The choroid plexus has the important function...
  
   (brain)
• Colloid cyst
  Colloid cyst
  A colloid cyst is a cyst containing gelatinous material in the brain. It is almost always found just posterior to the foramen of Monro in the anterior aspect of the third ventricle, originating from the roof of the ventricle. Because of its location, it can cause obstructive hydrocephalus and...
  
  
• Cysticercal cyst
  Cysticercosis
  Cysticercosis refers to tissue infection after exposure to eggs of Taenia solium, the pork tapeworm. The disease is spread via the fecal-oral route through contaminated food and water, and is primarily a food borne disease. After ingestion the eggs pass through the lumen of the intestine into the...
  
   (the larval stage of Taenia sp. (Crain's backs))
• Dentigerous cyst
  Dentigerous Cyst
  A dentigerous cyst or Follicular Cyst is an odontogenic cyst - thought to be of developmental origin - associated with the crown of an unerupted tooth. The cyst cavity is lined by epithelial cells derived from the reduced enamel epithelium of the tooth forming organ...
  
   (associated with the crowns of non-erupted teeth)
• Dermoid cyst
  Dermoid cyst
  A dermoid cyst is a cystic teratoma that contains developmentally mature skin complete with hair follicles and sweat glands, sometimes clumps of long hair, and often pockets of sebum, blood, fat, bone, nails, teeth, eyes, cartilage, and thyroid tissue. Because it contains mature tissue, a dermoid...
  
   (ovaries, testes, many other locations from head to tailbone)
• Epididymal cyst (found in the vessels attached to the testes)
• Ganglion cyst
  Ganglion cyst
  A ganglion cyst, also known as a bible cyst, is a swelling that often appears on or around joints and tendons in the hand or foot. The size of the ganglion or cyst can vary over time. It is most frequently located around the dorsum of the wrist and on the fingers...
  
   (hand/foot joints and tendons)
• Glandular odontogenic cyst
  Glandular odontogenic cyst
  The glandular odontogenic cyst is a rare odontogenic cyst. In 85% of cases, it is found in the mandible, especially in anterior areas. It is more common in adults in their fifth and sixth decades. On radiographs, it can appear as a unilocular or multilocular radiolucency...
  
  
• Glial cyst (in the brain)
• Gartner's duct
  Gartner's duct
  Gartner's duct is a potential embryological remnant in human female development of the mesonephric ducts in the development of the urinary and reproductive organs...
  
   cyst (vaginal or vulvar cyst of embryological origin)
• Hydatid cyst (larval stage of Echinococcus granulosus (tapeworm))
• Hydrocele
  Hydrocele
  A hydrocoele denotes a pathological accumulation of serous fluid in a body cavity. It can also be noted as a minor malformation of newborns due to high levels of lead in the mother's blood during pregnancy....
  
   (testicle
  Testicle
  The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
  
  )
• Keratocyst
  Odontogenic keratocyst
  A keratocystic odontogenic tumour , abbreviated KCOT, is a rare and benign but locally aggressive developmental cystic neoplasm. It most often affects the posterior mandible....
  
   (in the jaws, these can appear solitary or associated with the Gorlin-Goltz or Nevoid basal cell carcinoma syndrome
  Nevoid basal cell carcinoma syndrome
  Nevoid basal cell carcinoma syndrome , also known as basal cell nevus syndrome, multiple basal cell carcinoma syndrome, Gorlin syndrome, and Gorlin–Goltz syndrome, is an inherited medical condition involving defects within multiple body systems such as the skin, nervous system, eyes, endocrine...
  
  . The latest World Health Organization
  World Health Organization
  The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
  
   classification considers Keratocysts as tumors rather than cysts)
• Liver cystic disease
  Polycystic liver disease
  Polycystic liver disease usually describes the presence of multiple cysts scattered throughout normal liver tissue, in association with polycystic kidney disease.-Pathophysiology:Associations with PRKCSH and SEC63 have been described....
  
  
• Meibomian cyst
  Chalazion
  A chalazion , also known as a meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of a blocked meibomian gland, usually on the upper eyelid. Chalazia differ from styes in that they are subacute and usually painless nodules...
  
   (eyelid)
• Mucoid cyst (ganglion cysts of the digits)
• Mucous cyst of the oral mucosa
• Nabothian cyst
  Nabothian cyst
  A nabothian cyst is a mucus-filled cyst on the surface of the cervix. They are most often caused when stratified squamous epithelium of the ectocervix grows over the simple columnar epithelium of the endocervix...
  
   (cervix)
• Nasolabial duct cyst
• Odontogenic cyst
  Odontogenic cyst
  Odontogenic cyst is a closed sac, having a distinct membrane derived from rests of odontogenic epithelium. It may contain air, fluids, or semi-solid material. Intra-bony cysts are most common in the jaws, because the mandible and maxilla are the only bones with epithelial components. That...
  
   (teeth)
• Ovarian cyst
  Ovarian cyst
  An ovarian cyst is any collection of fluid, surrounded by a very thin wall, within an ovary. Any ovarian follicle that is larger than about two centimeters is termed an ovarian cyst. An ovarian cyst can be as small as a pea, or larger than an orange....
  
   (ovaries, functional and pathological)
• Pancreatic cyst
• Paradental cyst
  Paradental cyst
  Paradental cysts constitute a family of inflammatory odontogenic cyst, that typically appear in relation to crown or root of partially erupted molar tooth...
  
  
• Parapelvic cyst (kidney)
• Paratubal cyst (fallopian tube)
• Periapical cyst
  Periapical cyst
  The periapical cyst is the most common odontogenic cyst. It is caused by pulpal necrosis secondary to dental caries or trauma. The cyst lining is derived from the cell rests of Malassez. Usually, the periapical cyst is asymptomatic, but a secondary infection can cause pain...
  
   (The periapical cyst, otherwise 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
  Pilonidal cyst
  A pilonidal cyst, also referred to as a pilonidal abscess, pilonidal sinus or sacrococcygeal fistula, is a cyst or abscess near or on the natal cleft of the buttocks that often contains hair and skin debris.-Etymology:...
  
   (skin infection near tailbone)
• Renal cyst
  Renal cyst
  A renal cyst is a fluid collection in the kidney. There are several types based on the Bosniak classification. The majority are benign, simple cysts that can be monitored and not intervened upon...
  
   (kidneys)
• Polycystic ovary syndrome
  Polycystic ovary syndrome
  Polycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....
  
  
• Pineal gland cyst
  Pineal gland cyst
  A pineal gland cyst is a benign cyst in the pineal gland, a small endocrine gland in the brain. Historically, these fluid-filled bodies appeared on 1-4% of magnetic resonance imaging brain scans, but were more frequent at death, seen in 21-41% of autopsies. But a 2007 study by Pua et al...
  
  
• Radicular cyst (associated with the roots of non-vital teeth, also known as Periapical cyst
  Periapical cyst
  The periapical cyst is the most common odontogenic cyst. It is caused by pulpal necrosis secondary to dental caries or trauma. The cyst lining is derived from the cell rests of Malassez. Usually, the periapical cyst is asymptomatic, but a secondary infection can cause pain...
  
  )
• Residual cyst
• Sebaceous cyst
  Sebaceous cyst
  A sebaceous cyst is a term that loosely refers to either epidermoid cysts or pilar cysts . Because an epidermoid cyst originates in the epidermis and a pilar cyst originates from hair follicles, by definition, neither type of cyst is strictly a sebaceous cyst...
  
   (sac below skin)
• Spermatocele
  Spermatocele
  Spermatocele is a retention cyst of a tubule of the rete testis or the head of the epididymis distended with barely watery fluid that contains spermatozoa. Spermatoceles are the most common cystic condition encountered within the scrotum. They vary in size from several millimeters to many...
  
   (testicle
  Testicle
  The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
  
  )
• Tarlov cyst
  Tarlov cyst
  Tarlov cysts, also known as perineurial cysts, are cerebrospinal-fluid-filled sacs located in the spinal canal of the S1-to-S4 region, of the spinal cord, and can be distinguished from other meningeal cysts by their nerve-fiber-filled walls. Tarlov cysts are defined as cysts formed within the...
  
   (spine)
• Trichilemmal cyst
  Trichilemmal cyst
  A trichilemmal cyst, also known as a wen, pilar cyst or isthmus-catagen cyst, is a common cyst that forms from a hair follicle. They are most often found on the scalp. The cysts are smooth, mobile and filled with keratin, a protein component found in hair, nails, and skin. They may or may not be...
  
   – Same as a pilar cyst. A familial cyst of the scalp.
• Vocal fold cyst
  Vocal fold cyst
  Vocal fold cysts are collections of fluid in sac-like formations on the vocal folds.Cysts can deteriorate the quality of human speech production, causing diplophonia, a condition where the vocal cords produce multiple tones at the same time, or dysphonia, an impaired quality of voice typically...
  
  

Cystic fibrosis

Despite being described in 1938 as the microscopic

Microscopic

The microscopic scale is the scale of size or length used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...

 appearance of cysts in the pancreas, cystic fibrosis

Cystic fibrosis

Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...

 is an example of a genetic disorder

Genetic disorder

A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

 whose name is related to fibrosis of the cystic duct

Cystic duct

The cystic duct is the short duct that joins the gall bladder to the common bile duct. It usually lies next to the cystic artery. It is of variable length...

 and does not involve actual cysts.

Cystic neoplasm

Most cysts in the body are benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

 (dysfunctional) tumors, the result of plugged ducts or other natural body outlets for secretions. However sometimes these masses are considered neoplasm:

• Dermoid cyst
  Dermoid cyst
  A dermoid cyst is a cystic teratoma that contains developmentally mature skin complete with hair follicles and sweat glands, sometimes clumps of long hair, and often pockets of sebum, blood, fat, bone, nails, teeth, eyes, cartilage, and thyroid tissue. Because it contains mature tissue, a dermoid...
  
  
• Keratocyst
  Odontogenic keratocyst
  A keratocystic odontogenic tumour , abbreviated KCOT, is a rare and benign but locally aggressive developmental cystic neoplasm. It most often affects the posterior mandible....
  
  
• Calcifying odotogenic cyst

Treatment

Treatment ranges from simple enucleation

Enucleation (surgery)

As a general surgical technique, enucleation refers to the surgical removal of a mass without cutting into or dissecting it.-Removal of the eye:Enucleation refers to removal of the eyeball itself, while leaving surrounding tissues intact....

 of the cyst to curettage

Curettage

Curettage, in medical procedures, is the use of a curette to remove tissue by scraping or scooping.Curettages are also a declining method of abortion. It has been replaced by vacuum aspiration over the last decade....

 to resection

Resection

Resection may refer to:*Segmental resection , the partial removal of an organ or other body structure*Resection , a means of establishing a location...

. There are cysts, e.g. buccal bifurcation cyst

Buccal bifurcation cyst

Buccal bifurcation cyst is an inflammatory odontogenic cyst, of the paradental cysts family, that typically appears in the buccal bifurcation region of the mandibular first molars in the second half of the first decade of life...

 with self-resolation nature, in which close observation only can be employed unless the cyst is infected

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

 and symptomatic.

Related structures

A pseudocyst

Pseudocyst

Pseudocysts are like cysts, but lack epithelial or endothelial cells. Initial management consists of general supportive care. Symptoms and complications caused by pseudocysts require surgery. CT scans are used for initial imaging of cysts, and endoscopic ultrasounds are used in differentiating...

 is collection without a distinct membrane.

A syrinx

Syrinx (medicine)

In medicine, a syrinx is a rare, fluid-filled neuroglial cavity within the spinal cord , in the brain stem , or in the nerves of the elbow, usually in a young age.-Etymology:...

 in the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 or brainstem is sometimes inaccurately referred to as a cyst.

External links

• "Cyst Symptoms and Causes" by Melissa Conrad Stöppler, MD and William C. Shiel, Jr., MD, FACP, FACR.