A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

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 Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

is called an

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...

, 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-related cysts are formed as a defense mechanism for the body following the development of mutations that lead to an uncontrolled cellular division. Once that mutation has occurred, the affected cells divide incessantly and become cancerous, forming a tumor. 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 vessels, from which they receive nourishment before being contained. Once that happens, the capsule becomes useless, and the tumor may advance from benign to cancerous. Some cysts are neoplastic, and thus are called cystic tumors. Many types of cysts are not neoplastic, they are

dysplastic Dysplasia is any of various types of abnormal growth or development of cells (microscopic scale) or organs (macroscopic scale), and the abnormal histology or anatomical structure(s) resulting from such growth. Dysplasias on a mainly microscopic ...

or metaplastic. ''Pseudocysts'' are similar to cysts in that they have a sac filled with fluid, but lack an epithelial 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 ( epithelial or endothelial cells). A ''

syrinx In classical Greek mythology, Syrinx (Greek Σύριγξ) was a nymph and a follower of Artemis, known for her chastity. Pursued by the amorous god Pan, she ran to a river's edge and asked for assistance from the river nymphs. In answer, sh ...

'' in the spinal cord or

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 cont ...

is sometimes inaccurately referred to as a "cyst".

Cysts by location

Female reproductive system

Nabothian cyst A nabothian cyst (or nabothian follicle) is a mucus-filled cyst on the surface of the cervix. They are most often caused when stratified squamous epithelium of the ectocervix (portion nearest to the vagina) grows over the simple columnar epithe ...

(on the surface of the cervix) *

Ovarian cyst An ovarian cyst is a fluid-filled sac within the ovary. Often they cause no symptoms. Occasionally they may produce bloating, lower abdominal pain, or lower back pain. The majority of cysts are harmless. If the cyst either breaks open or causes ...

(ovary) *

Paratubal cyst Paraovarian cysts or paratubal cysts are epithelium-lined fluid-filled cysts in the adnexa adjacent to the fallopian tube and ovary. The terms are used interchangeably, and depend on the location of the cyst. Topic Completed: 1 July 2013. Minor c ...

(in front of fallopian tube behind the ovary) Relative incidences of ovarian cysts

* Vaginal cysts **

Gartner's duct cyst A Gartner's duct cyst (sometimes incorrectly referred to as ''vaginal inclusion cyst'') is a benign vaginal cyst that originates from the Gartner's duct, which is a vestigial remnant of the mesonephric duct (wolffian duct) in females. They are typi ...

(lateral to vaginal wall) ** Bartholin's cyst (at

vaginal introitus In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen. ...

) ** 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 Rete tubular ectasia , also known as cystic transformation of rete testis is a benign condition, usually found in older men, involving numerous small, tubular cystic structures within the rete testis. Presentation It is usually found in men older ...

(within the rete testis) *

Epididymal cyst An epididymal cyst is a cyst of the epididymis containing serous liquid. They are difficult to differentiate from a spermatocele except by aspiration, since a spermatocele contains milky-appearing sperm Sperm is the male reproductive cell, or ...

(in the

epididymis The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...

) * Hydrocele testis ( testicle): clear fluid within the cavum vaginale * Spermatocele ( testicle): fluid within the head of epididymis

Cutaneous and subcutaneous

* Acne cyst – Pseudocysts associated with cystic acne - an inflammatory nodule with or without an associated epidermoid inclusion 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 meningeal layers that cover the brain and the ...

(between the surface of the brain and the

cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

base or on the arachnoid membrane) * Epidermoid cyst *

Myxoid cyst A myxoid cyst is a cutaneous condition often characterized by nail plate depression and grooves. See also * Scleroderma * List of cutaneous conditions * List of radiographic findings associated with cutaneous conditions Many conditions of o ...

(cutaneous condition often characterized by nail plate depression and grooves) *

Pilar 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, nails, skin, and horns. Trichilemmal cysts are clin ...

(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 kera ...

– 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, nails, skin, and horns. Trichilemmal cysts are clin ...

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

Head and neck

* Odontogenic cyst *

Ceruminous Ceruminous glands are specialized sudoriferous glands (sweat glands) located subcutaneously in the external auditory canal, in the outer 1/3. Ceruminous glands are simple, coiled, tubular glands made up of an inner secretory layer of cells and an ou ...

cyst (ear) * Chalazion cyst (eyelid) *

Mucous cyst of the oral mucosa Oral mucocele (also mucous extravasation cyst, mucous cyst of the oral mucosa, and mucous retention and extravasation phenomena.) is a condition caused by two related phenomena - mucus extravasation phenomenon and mucous retention cyst. Mucous e ...

Nasolabial cyst This nasolabial cyst, also known as a nasoalveolar cyst, is located superficially in the soft tissues of the upper lip. Unlike most of the other developmental cysts, the nasolabial cyst is an example of an extraosseous cyst, one that occurs outsi ...

* Thyroglossal cyst *

Vocal fold cyst Vocal fold cysts (also known as ''vocal cord cysts'') are benign masses of the membranous vocal folds. These cysts are enclosed, sac-like structures that are typically of a yellow or white colour. They occur unilaterally on the midpoint of the med ...

Chest

* Fibrous cyst (

breast cyst A breast cyst is a cyst, a fluid-filled sac, within the breast. One breast can have one or more cysts. They are 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 ...

) *

Pulmonary cyst A focal lung pneumatosis, is an enclosed pocket of air or gas in the lung and includes blebs, bullae, pulmonary cysts, and lung cavities. Blebs and bullae can be classified by their wall thickness. * A bleb has a wall thickness of less than 1 mm ...

(air pocket in the lung) *

Pericardial cyst A pericardial cyst is an uncommon benign dilatation of the pericardial sac surrounding the heart. It can lead to symptoms by compressing nearby structures, but is usually asymptomatic. Pericardial cysts can be congenital or acquired, and they are t ...

(abnormal dilatation of pericardium)

Abdomen

Liver cyst The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...

s ** Simple cysts ** Hydatid cysts ** Biliary cystadenoma ** Biliary cystadenocarcinoma ** Polycystic liver disease *

Adrenal The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which ...

cyst (glands located above the kidneys) - It is a rare disease, affecting 0.06 to 0.18% of

autopsy An autopsy (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 death or to evaluate any di ...

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 A pancreatic cyst is a fluid filled sac within the pancreas. Causes range from benign to malignant. Pancreatic cysts can occur in the setting of pancreatitis, though they are only reliably diagnosed 6 weeks after the episode of acute pancreati ...

* 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 Enteric duplication cysts, sometimes simply called duplication cysts, are rare congenital malformations of the gastrointestinal tract. They most frequently occur in the small intestine, particularly the ileum, but can occur anywhere along the gastro ...

Central nervous system

Choroid plexus cyst Choroid plexus cysts (CPCs) are cysts that occur within choroid plexus of the brain. They are the most common type of intraventricular cyst, occurring in 1% of all pregnancies. It is believed that many adults have one or more tiny CPCs. The feta ...

* Colloid cyst *

Pineal gland cyst A pineal gland cyst is a usually benign (non-malignant) cyst in the pineal gland, a small endocrine gland in the brain. Historically, these fluid-filled bodies appeared on of magnetic resonance imaging (MRI) brain scans, but were more frequently d ...

(in the

pineal gland The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep, sleep patterns in both circadian rhythm, circ ...

in the brain) *

Glial cyst Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form myel ...

* 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 pai ...

, a benign bone tumor with a radiographic cystic appearance. *

Baker's cyst A Baker's cyst, also known as a popliteal cyst, is a type of fluid collection behind the knee. Often there are no symptoms. If symptoms do occur these may include swelling and pain behind the knee, or knee stiffness. If the cyst breaks open, pain ...

or popliteal cyst (behind the knee joint) *

Mucoid cyst A myxoid cyst is a cutaneous condition often characterized by nail plate depression and grooves. See also * Scleroderma * List of cutaneous conditions * List of radiographic findings associated with cutaneous conditions Many conditions of o ...

(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 depres ...

(an anatomic variant with radiographic cystic appearance in the posterior mandible) * 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 A ganglion cyst is a fluid-filled bump associated with a joint or tendon sheath. It most often occurs at the back of the wrist, followed by the front of the wrist. Onset is often over several months, typically with no further symptoms. Occasional ...

(hand and foot joints and tendons) *

(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 An odontogenic keratocyst is a rare and benign but locally aggressive developmental cyst. It most often affects the posterior mandible and most commonly presents in the third decade of life. Odontogenic keratocysts make up around 19% of jaw cysts. ...

* Calcifying odontogenic cyst

Treatment

Treatment ranges from simple enucleation of the cyst to curettage to resection. There are cysts—e.g.,

buccal bifurcation cyst Buccal bifurcation cyst is an inflammation, inflammatory odontogenic cyst, of the paradental cysts family, that typically appears in the Cheek, buccal bifurcation region of the human mandible, mandibular first molar (tooth), molars in the second ...

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

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...

atic.

Cystic fibrosis

Despite being described in 1938 as "the microscopic appearance of cysts in the pancreas",

cystic fibrosis Cystic fibrosis (CF) is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. O ...

is an example of a genetic disorder whose name is related to fibrosis of the cystic duct (which serves the gallbladder) 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 and the gallbladder, neither of which involve cysts.

References

External links

"Cyst Symptoms and Causes"
by Melissa Conrad Stöppler, MD and William C. Shiel Jr., MD, FACP, FACR. {{Authority control Gross pathology Dermatologic terminology