A cyst is a closed sac, having a distinct

envelope An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter (message), letter or Greeting card, card. Traditional envelopes are made from sheets of paper cut to one o ...

and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble); however, the distinguishing aspect of a cyst is that the cells forming the "shell" of such a sac are distinctly abnormal (in both appearance and behaviour) when compared with all surrounding cells for that given location. A cyst may contain air, fluids, or semi-solid material. A collection of pus is called an

abscess An abscess is a collection of pus that has built up within the tissue of the body, usually caused by bacterial infection. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pre ...

, not a cyst. Once formed, a cyst may resolve on its own. When a cyst fails to resolve, it may need to be removed surgically, but that would depend upon its type and location.

Cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

-related cysts are formed as a defense mechanism for the body following the development of

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

s that lead to an uncontrolled cellular division. Once that mutation has occurred, the affected cells divide incessantly and become cancerous, forming a

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

. The body encapsulates those cells to try to prevent them from continuing their division and contain the tumor, which becomes known as a cyst. That said, the cancerous cells still may mutate further and gain the ability to form their own

blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...

s, from which they receive nourishment before being contained. Once that happens, the capsule becomes useless, and the tumor may advance from

benign Malignancy () is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

to cancerous. Some cysts are neoplastic, and thus are called cystic tumors. Many types of cysts are not neoplastic, they are dysplastic or metaplastic. ''Pseudocysts'' are similar to cysts in that they have a sac filled with fluid, but lack an

epithelial Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

lining.

Terminology

* ''microcyst – a'' small cyst that requires magnification to be seen * ''macrocyst –'' a cyst that is larger than usual or compared to others

Related structures

A '' pseudocyst'' is very similar to a cyst, but is a collection of cells without a distinct membrane (

or endothelial cells). A ''

syrinx In classical Greek mythology, Syrinx () was an Arcadian nymph and a follower of Artemis, known for her chastity. Being pursued by Pan, she fled into the river Ladon, and at her own request was metamorphosed into a reed from which Pan then mad ...

'' in the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

is sometimes inaccurately referred to as a "cyst".

Cysts by location

Female reproductive system

* Nabothian cyst (on the surface of the cervix) * Ovarian cyst (ovary) * Paratubal cyst (in front of fallopian tube behind the ovary) Relative incidences of ovarian cysts

* Vaginal cysts ** Gartner's duct cyst (lateral to vaginal wall) ** Bartholin's cyst (at vaginal introitus) ** Skene's duct cyst (beside the urinary meatus) **Ectopic ureterocoele (around the urinary meatus) **Urethral diverticulum (in front of vaginal wall)

Male reproductive system

* Rete tubular ectasia (within the rete testis) * Epididymal cyst (in the

epididymis The epididymis (; : epididymides or ) is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles. It is a single, narrow, tightly coiled tube in adult humans, in length; ...

) * Hydrocele testis (

testicle A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, p ...

): clear fluid within the cavum vaginale * Spermatocele (

): fluid within the head of epididymis

Cutaneous and subcutaneous

Acne Acne ( ), also known as ''acne vulgaris'', is a long-term Cutaneous condition, skin condition that occurs when Keratinocyte, dead skin cells and Sebum, oil from the skin clog hair follicles. Typical features of the condition include comedo, ...

cyst – Pseudocysts associated with cystic acne - an inflammatory nodule with or without an associated epidermoid inclusion cyst * Arachnoid cyst (between the surface of the brain and the cranial base or on the arachnoid membrane) * Epidermoid cyst * Myxoid cyst (cutaneous condition often characterized by nail plate depression and grooves) * Pilar cyst (cyst of the scalp) * Pilonidal cyst (skin infection near tailbone) *

Sebaceous cyst A sebaceous cyst is a term commonly used to refer to either: * Epidermoid cysts (also termed epidermal cysts, infundibular cyst) * Pilar cysts (also termed trichelemmal cysts, isthmus-catagen cysts) Both of the above types of cysts contain ...

– sac below skin *

Trichilemmal cyst A trichilemmal cyst (or pilar cyst) is a common cyst that forms from a hair follicle, most often on the scalp, and is smooth, mobile, and filled with keratin, a protein component found in hair, nail (anatomy), nails, skin, and horn (anatomy), ho ...

– same as a pilar cyst, a familial cyst of the scalp

Head and neck

* Odontogenic cyst * Ceruminous cyst (ear) * Chalazion cyst (eyelid) * Mucous cyst of the oral mucosa * Nasolabial cyst * Nasopalatine duct cyst * Thyroglossal cyst * Vocal fold cyst

Chest

* Fibrous cyst ( breast cyst) * Pulmonary cyst (air pocket in the lung) * Pericardial cyst (abnormal dilatation of

pericardium The pericardium (: pericardia), also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong inelastic connective tissue (fibrous pericardium), ...

)

Abdomen

Liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

cysts ** Simple cysts ** Hydatid cysts ** Biliary cystadenoma ** Biliary cystadenocarcinoma ** Polycystic liver disease * Adrenal cyst (glands located above the kidneys) - It is a rare disease, affecting 0.06 to 0.18% of

autopsy An autopsy (also referred to as post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of deat ...

studies. It constitutes 5.4 to 6.0% of adrenal gland diseases. There are five major types of adrenal cysts: simple or endothelial cysts, true or epithelial cysts, pseudocysts, parasitic cysts, and cysts not classified elsewhere. 7% of the cysts can be malignant. * Renal cyst (kidneys) * Pancreatic cyst * Peritoneal inclusion cyst (lining of the abdominal cavity) - It is a cluster of fluid-filled cysts lining the abdominal cavity of reproductive age women with a history of pelvic, abdominal surgeries, or abdominal inflammation. Those affected maybe presented with an abdominal, pelvic, lower back that lasted for months. * Enteric duplication cyst

Central nervous system

* Choroid plexus cyst *

Colloid cyst A colloid cyst is a non-malignant tumor in the brain. It consists of a gelatinous material contained within a membrane of epithelial tissue. It is almost always found just posterior to the foramen of Monro in the anterior aspect of the third v ...

* Pineal gland cyst (in the

pineal gland The pineal gland (also known as the pineal body or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. It produces melatonin, a serotonin-derived hormone, which modulates sleep, sleep patterns following the diurnal c ...

in the brain) * Glial cyst * Tarlov cyst (spinal canal)

Musculoskeletal system

Aneurysmal bone cyst Aneurysmal bone cyst (ABC) is a non-cancerous bone tumor composed of multiple varying sizes of spaces in a bone which are filled with blood. The term is a misnomer, as the lesion is neither an aneurysm nor a cyst. It generally presents with ...

, a benign bone tumor with a radiographic cystic appearance. * Baker's cyst or popliteal cyst (behind the knee joint) * Mucoid cyst (ganglion cysts of the digits) *

Stafne static bone cyst The Stafne defect (also termed Stafne's idiopathic bone cavity, Stafne bone cavity, Stafne bone cyst (misnomer), lingual mandibular salivary gland depression, lingual mandibular cortical defect, latent bone cyst, or static bone cyst) is a depre ...

(an anatomic variant with radiographic cystic appearance in the posterior

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

) * Subchondral cyst (cysts near the bony joints)

Seen in various locations

* Dermoid cyst (seen in ovaries, testes, and many other locations, from head to tailbone) * Ganglion cyst (hand and foot joints and tendons) * Mucoid cyst (ganglion cysts of the digits)

Infectious cysts

* Cysticercal cyst – an infection due to the larval stage of ''Taenia sp.'' (Crain's backs) * Hydatid cyst – an infection in the liver or other parts of the body due to the larval stage of ''Echinococcus granulosus'' ( tapeworm)

Neoplastic cysts

* 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—that resolve on their own, in which just close observation may be employed, unless it is infected and

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

atic.

Cystic fibrosis

Despite being described in 1938 as "the

microscopic The microscopic scale () is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded as the scale betwe ...

appearance of cysts in the pancreas",

cystic fibrosis Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of Sputum, mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably ''Staphy ...

is an example of a

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders ...

whose name is related to fibrosis of the cystic duct (which serves the

gallbladder In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow Organ (anatomy), organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath t ...

) and does not involve cysts. This is just one example of how the Greek root ''cyst-'', which simply means a fluid-filled sac, also is found in medical terms that relate to the

urinary bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the Kidney (vertebrates), kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the ...

and the

, neither of which involve cysts.

References

External links

* * {{Authority control Dermatologic terminology Gross pathology