keratin cyst

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keratin cyst

an epithelial cyst containing keratin. Also called keratinous cyst.


(sist) [Gr. kystis, bladder, sac]
1. A closed sac or pouch with a definite wall, containing fluid, semifluid, or solid material. It is usually an abnormal structure resulting from developmental anomalies, obstruction of ducts, or parasitic infection.
2. In biology, a structure formed by and enclosing certain organisms in which they become inactive, such as the cyst of certain protozoans or of the metacercariae of flukes.

adventitious cyst

A cyst formed around a foreign body.

alveolar cyst

Dilation and rupture of pulmonary alveoli to form air cysts.

apical cyst

A cyst near the apex of the root of a nonvital tooth.

arachnoid cyst

An abnormal collection of cerebrospinal fluid within the arachnoid membrane. The cysts may compress nearby structures within the brain. In infants, they may cause headaches, altered mental status, learning disabilities, or enlargement of the head. In adults, they are an occasional cause of epilepsy.

Baker cyst

See: Baker cyst.

Bartholin cyst

See: Bartholin, Caspar (the younger)

blood cyst


blue dome cyst

1. A mammary cyst containing light, straw-colored fluid, which appears blue when seen through the surrounding tissue.
2. A small dark-blue cyst in the vagina caused by retained menstrual blood seen in endometriosis.

branchial cyst

Cervical cyst.

bone cyst

A cystic mass in bone, usually a normal variant or a benign tumor.

Boyer cyst

See: Boyer cyst

cervical cyst

A closed epithelial sac derived from a branchial groove of its corresponding pharyngeal pouch. Synonym: branchial cyst

chocolate cyst

An ovarian cyst with darkly pigmented gelatinous contents.

colloid cyst

A cyst with gelatinous contents.

complex cyst

A cyst that consists of solid material and fluid-filled cavities; it may have walls of tissue inside it or internal echoes. When a complex cyst is identified on ultrasound, surgical removal is generally indicated to exclude malignancy.

congenital cyst

A cyst present at birth and resulting from abnormal development, such as a dermoid cyst, imperfect closure of a structure as in spina bifida cystica, or nonclosure of embryonic clefts, ducts, or tubules, such as cervical cysts.

daughter cyst

A cyst growing out of the walls of another cyst.

dental cyst

A cyst that forms from any of the odontogenic tissues.

dentigerous cyst

A fluid-filled, epithelial-lined cyst usually surrounding the crown of a tooth that is erupting or has not yet erupted. The tooth normally erupts through the cyst without treatment. Synonym: eruption cyst; follicular cyst; follicular odontoma

dermoid cyst

1. An ovarian teratoma.
2. A nonmalignant cystic tumor containing elements derived from the ectoderm, such as hair, teeth, or skin. These tumors occur frequently in the ovary but may develop in other organs such as the lungs.

distention cyst

A cyst formed in a natural enclosed cavity, such as a follicular cyst of the ovary.

echinococcus cyst

Hydatid cyst.

endometrial cyst

An ovarian cyst or tumor lined with endometrial tissue, usually seen in ovarian endometriosis.

epidermoid cyst

A cyst filled with keratin, sebum, and skin debris that may form on the scalp, the back of the neck, or the axilla. It is benign andf can be removed surgically. Synonym: sebaceous cyst

eruption cyst

Dentigerous cyst.

extravasation cyst

A cyst arising from hemorrhage or escape of other body fluids into tissues.

exudation cyst

A cyst caused by trapping of an exudate in a closed area.
Enlarge picture
FOLLICULAR CYST: Follicular cysts seen on ultrasonography of the thyroid gland.

follicular cyst

A cyst arising from a follicle, as a follicular cyst of the thyroid gland, the ovary, or a forming tooth. Synonym: dentigerous cyst See: illustration

ganglion cyst

ganglion (2)

Gartner cyst

See: Gartner cyst

Gorlin cyst

See: Gorlin cyst

hydatid cyst

A cyst formed by the growth of the larval form of Echinococcus granulosus, usually in the liver. Synonym: echinococcus cyst

implantation cyst

A cyst resulting from displacement of portions of the epidermis, as may occur in injuries.

intraligamentary cyst

A cystic formation between the layers of the broad ligament.

involutional cyst

A cyst occurring in the normal involution of an organ or structure, as in the mammary gland.

keratin cyst

A cyst containing keratin.

cysts of liver

Simple cysts, usually small and single; or hydatid cysts; or cysts associated with cystic disease of the liver, a rare condition usually associated with congenital cystic kidneys. See: Echinococcus granulosus; hydatid

meibomian cyst


meniscus cyst

A fluid-filled cyst often associated with a degenerative horizontal meniscal tear, more frequently seen in the lateral meniscus of the knee. This ganglion-like cyst may present with a palpable mass at the joint line of the knee and can be visualized by magnetic resonance imaging.

morgagnian cyst

See: Morgagni, Giovanni B

Morgagni cyst

See: Morgagni, Giovanni B

mother cyst

A hydatid cyst enveloping smaller ones.

mucous cyst

A retention cyst composed of mucus.

nabothian cyst

A cyst caused by closure of the ducts of the nabothian glands in the uterine cervix as a result of chronic cervicitis.

odontogenic cyst

A cyst associated with the teeth, such as a dentigerous or radicular cyst.

ovarian cyst

A fluid-filled cyst that develops in the ovary and consists of one or more chambers. The main types of cysts are follicular cysts, the corpus luteum, teratoma, and endometrioma. The patient's primary complaint is generally pelvic pain or pain during intercourse. The cysts may be palpated during bimanual examination but are diagnosed by ultrasound. Many cysts resolve spontaneously. Although nonmalignant, the cyst may have to be removed surgically because of twisting of the pedicle, which causes gangrene, or because of pressure.
See: polycystic ovary syndrome

parasitic cyst

A cyst enclosing the larval form of certain parasites, such as the cysticercus or hydatid of tapeworms or the larva of certain nematodes, i.e., Trichinella.

parovarian cyst

A cyst of the parovarium.

periapical cyst

Radicular cyst.

pilar cyst

An epithelial cyst with a wall that resembles the follicular epithelium. It is filled with a homogeneous mixture of keratin and lipid.
Synonym: trichilemma cyst

pilonidal cyst

A cyst most often in the sacrococcygeal region, usually at the upper end of the intergluteal cleft. It is due to a developmental defect that permits epithelial tissue to be trapped below the skin or may be acquired. This type of cyst may become symptomatic in early adulthood when an infected draining sinus forms.
Synonym: pilonidal fistula

popliteal cyst

Baker cyst.

porencephalic cyst

An anomalous cavity of the brain that communicates with the ventricular system.

proliferative cyst

A cyst lined with epithelium that proliferates, forming projections that extend into the cavity of the cyst.

radicular cyst

A necrotic, inflammatory cyst that develops at the root of a nonvital tooth. The cyst is attached to the root of the tooth and may be lateral to it if the cyst is associated with a lateral pulp canal.
Synonym: periapical cyst; root-end cyst

retention cyst

A cyst retaining the secretion of a gland, as in a mucous or sebaceous cyst.

root-end cyst

Radicular cyst.

sebaceous cyst

Epidermoid cyst.

seminal cyst

A cyst of the epididymis, ductus deferens, or other sperm-carrying ducts that contain semen.

suprasellar cyst

A cyst of the hypophyseal stalk just above the floor of the sella turcica. Its wall is frequently calcified or ossified.

synovial cyst

Accumulation of synovia in a bursa, synovial crypt, or sac of a synovial hernia, causing a tumor.

theca-lutein cyst

Benign enlargement of the Graafian follicle, typically occurring in pregnancies (particularly in multiple pregnancies) or in other conditions that cause markedly elevated levels of serum human chorionic gonadotropin (HCG) levels, e.g., molar pregnancies or choriocarcinomas.
Synonym: hyperreactio luteinalis

trichilemma cyst

Pilar cyst.

tubo-ovarian cyst

An ovarian cyst that ruptures into the lumen of an adherent uterine tube.

unilocular cyst

A cyst containing only one cavity.

vaginal cyst

A cyst in the vagina.

vitelline cyst

A congenital cyst of the gastrointestinal canal. Lined with ciliated epithelium, it is the remains of the omphalomesenteric duct.

wolffian cyst

A cyst lying in one of the broad ligaments of the uterus.


1. a closed epithelium-lined sac or capsule containing a liquid or semi-solid substance. Most cysts are harmless but they occasionally may change into malignant growths, become infected, or obstruct a gland. There are four main types of cysts: retention cysts, exudation cysts, embryonic cysts and parasitic cysts. See also specific locations and organs.
2. a stage in the life cycle of certain parasites, during which they are enveloped in a protective wall. See also cystic.

aneurysmal cyst
see bone cyst.
blood c's
these are found in the carcasses of poultry at meat inspection. They are small round cystic lesions containing blood. They are hemangiomas.
branchial cyst, branchiogenic cyst, branchiogenous cyst
one formed from an incompletely closed branchial cleft. See also branchial cyst.
cervical c's
retention cysts of glands in the uterine cervix in the cow, are palpable as fluctuating masses on rectal examination. Called also nabothian cyst or follicle.
chocolate cyst
one filled with hemosiderin following local hemorrhage.
cutaneous cyst
see epidermal cyst, dermoid cyst, follicular cyst, sebaceous cyst.
daughter cyst
one that develops within a parent cyst, e.g. hydatid cyst.
dentigerous cyst
see dental cyst.
echinococcus cyst
hydatid cyst.
embryonic cyst
one developing from bits of embryonic tissue that have been overgrown by other tissues, or from developing organs that normally disappear before birth. An example is a branchial cyst.
epidermal inclusion cyst
see epithelial inclusion.
exudation cyst
a cyst formed by the slow seepage of an exudate into a closed cavity.
fatty cyst
formed when fat accumulates in large amounts and the cells break down forming a central mass of lipid surrounded by a multinuclear rim.
follicular cyst
one due to occlusion of the duct of a follicle or small gland, especially one formed by enlargement of a graafian follicle as a result of accumulated transudate.
Gartner's duct cyst
see cystic gartner's ducts.
horn cyst
intracutaneous cystic accumulations of keratin. Seen in trichoepitheliomas and basal cell tumors. Called also keratin cyst.
hybrid cyst
one combining elements of epidermoid and trichilemmal cysts.
hydatid cyst
the larval stage (metacestode) of the tapeworms Echinococcus granulosus and E. multilocularis. See also hydatid disease.
inclusion cyst
see epidermal cyst.
interdigital c's
see pododermatitis; interdigital pyoderma.
keratin cyst
one arising in the pilosebaceous apparatus, lined by stratified squamous epithelium and containing largely macerated keratin and often sufficient sebum to render the contents greasy and often rancid.
lateral cervical cyst
see branchial cyst.
luteal c's
develop from ovarian follicles which fail to rupture but have a lining of luteal cells. Anestrus is the presenting clinical sign.
marine fish c's
worldwide occurrence in fish of round nodules in fibrous capsules; the cause is unknown.
meibomian cyst
mesenteric cyst
congenital, thin-walled cyst between the leaves of the mesentery; may enlarge and cause colic or even intestinal obstruction.
cyst mites
see laminosioptescysticola.
cyst of Morgagni
nabothian cyst
see cervical cyst (above).
orbital cyst
ovarian cyst
see cystic ovarian disease.
parasitic cyst
one forming around larval parasites (tapeworms, amebae, trichinae) that enter the body.
pseudohorn cyst
invagination of hyperplastic epidermis; not a true cyst.
retention cyst
a tumor-like accumulation of a secretion formed when the outlet of a secreting gland is obstructed. These cysts may develop in any of the secretory glands—the mammae, pancreas, kidney, salivary or sebaceous glands, and mucous membranes. See also renal retention cysts.
sarcosporidian c's
cylindrical cysts (schizonts) containing bradyzoites, found in the muscles of those infected with Sarcocystis spp.
subconjunctival cyst, conjunctival cyst
misplaced secretory tissue which causes a slowly enlarging, fluctuant subconjunctival mass.
uveal cyst
an acquired or congenital structure which may arise from the iris or the ciliary body. Visible as a mass attached to the iris or may be floating freely in the anterior chamber. Those arising from the ciliary body may not be visible. Seen most commonly in horses. See also iris cyst.
vitelline cyst
a congenital cyst lined with ciliated epithelium occurring along the gastrointestinal canal; the remains of the omphalomesenteric duct.


a scleroprotein which is the principal constituent of epidermis, hair, nails, horny tissues, and the organic matrix of the enamel of the teeth. Its solution is sometimes used in coating pills when the latter are desired to pass through the stomach unchanged.

keratin cyst
see horn cyst.
keratin pearl
see horn pearls.
keratin tag
see fibrovascular papilloma.
References in periodicals archive ?
No keratin cysts are reported in FBP, (20) whereas keratin cysts are seen in BFH, TE, and ICBCC.

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