meibomian cyst

cyst (sist)

1. bladder.

2. an abnormal closed epithelium-lined cavity in the body, containing liquid or semisolid material.

3. a stage in the life cycle of certain parasites, during which they are enveloped in a protective wall.

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adventitious cyst  one formed about a foreign body or exudate.

alveolar cysts  dilatations of pulmonary alveoli, which may fuse by breakdown of their septa to form pneumatoceles.

aneurysmal bone cyst  a benign, rapidly growing, osteolytic lesion, usually of childhood, characterized by blood-filled cystic spaces lined by bony or fibrous septa.

arachnoid cyst  a fluid-filled cyst between the layers of the leptomeninges, lined with arachnoid membrane, usually in the sylvian fissure.

Baker cyst  a swelling behind the knee due to escape of synovial fluid that has become enclosed in a sac or membrane.

Blessig cysts  cystic spaces formed at the periphery of the retina.

blue dome cyst  a benign retention cyst of the breast which shows a blue color.

Boyer cyst  an enlargement of the subhyoid bursa.

branchial cyst  one arising in the lateral aspect of the neck, from epithelial remnants of a branchial cleft (pharyngeal groove), usually between the second and third pharyngeal arches.

bronchogenic cyst  a congenital cyst, usually in the mediastinum or lung, arising from anomalous budding during formation of the tracheobronchial tree, lined with bronchial epithelium that may contain secretory elements.

chocolate cyst  one having dark, syrupy contents, resulting from collection of hemosiderin following local hemorrhage.

choledochal cyst  a congenital cystic dilatation of the common bile duct, which may cause pain in the right upper quadrant, jaundice, fever, or vomiting, or be asymptomatic.

congenital preauricular cyst  one due to imperfect fusion of the first and second branchial arches in formation of the auricle, communicating with an ear pit on the surface.

dentigerous cyst  a fluid-containing odontogenic cyst surrounding the crown of an unerupted tooth.

dermoid cyst  a teratoma, usually benign, characterized by mature ectodermal elements, having a fibrous wall lined with stratified epithelium, and containing keratinous material, hair, and sometimes material such as bone, tooth, or nerve tissue; found most often in the ovary.

duplication cyst  a congenital cystic malformation of the alimentary tract, consisting of a duplication of the segment to which it is adjacent, occurring anywhere from the mouth to the anus but most frequently affecting the ileum and esophagus.

echinococcus cyst  hydatid c.

enteric cyst , enterogenous cyst a cyst of the intestine arising or developing from a fold or pouch along the intestinal tract.

epidermal cyst  a benign cyst derived from the epidermis or the epithelium of a hair follicle; it is formed by cystic enclosures of epithelium within the dermis, filled with keratin and lipid-rich debris.

epidermal inclusion cyst  a type of epidermal cyst occurring on the head, neck, or trunk, formed by keratinizing squamous epithelium with a granular layer.

epidermoid cyst 

1. epidermal c.

2. a benign tumor formed by inclusion of epidermal elements, especially at the time of closure of the neural groove, and located in the skull, meninges, or brain.

epithelial cyst 

1. any cyst lined by keratinizing stratified squamous epithelium, found most often in the skin.

2. epidermal c.

exudation cyst  one formed by an exudate in a closed cavity.

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.

globulomaxillary cyst  one within the maxilla at the junction of the globular portion of the medial nasal process and the maxillary process.

hydatid cyst  the larval cyst stage of the tapeworms Echinococcus granulosus and E. multilocularis, containing daughter cysts with many scoleces.

keratinizing 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 or rancid.

lutein cyst  a cyst of the ovary developed from a corpus luteum.

median anterior maxillary cyst  one in or near the incisive canal, arising from proliferation of epithelial remnants of the nasopalatine duct.

median palatal cyst  one in the midline of the hard palate, between the lateral palatal processes.

meibomian cyst  a cyst of the meibomian gland, sometimes applied to a chalazion.

mucus retention cyst  a mucus-containing retention cyst caused by blockage of a salivary gland duct.

multilocular cyst 

1. a cyst containing several loculi or spaces.

2. a hydatid cyst with many small irregular cavities that may contain scoleces but generally little fluid.

3. a thick-walled cyst in the kidney, found in clusters and usually unilaterally. In children it contains blastema and may develop into a Wilms tumor.

myxoid cyst  a nodular lesion usually overlying an interphalangeal finger joint, consisting of focal mucinous degeneration of collagen of the dermis; not a true cyst, it lacks an epithelial wall and does not communicate with the underlying synovial space.

Naboth's cysts , nabothian cysts see under follicle.

nasoalveolar cyst , nasolabial cyst a fissural cyst arising outside the bones at the junction of the globular portion of the medial nasal process, lateral nasal process, and maxillary process.

odontogenic cyst  one derived from epithelium, usually containing fluid or semisolid material, which develops during various stages of odontogenesis; nearly always enclosed within bone.

osseous hydatid cysts  hydatid cysts formed by the larvae of Echinococcus granulosus in bone, which may become weakened and eroded by the exuberant growth.

parasitic cyst  one forming around larval parasites (tapeworms, amebas, trichinae), such as a hydatid cyst.

periapical cyst  a periodontal cyst involving the apex of an erupted tooth.

periodontal cyst  one in the periodontal ligament and adjacent structures, usually at the apex of the tooth (periapical c.).

pilar cyst  an epithelial cyst of the scalp, almost identical to an epidermal cyst, arising from the outer root sheath of the hair follicle.

piliferous cyst , pilonidal cyst a hair-containing sacrococcygeal dermoid cyst or sinus, often opening at a postanal dimple.

radicular cyst  an epithelium-lined sac at the apex of a tooth.

Rathke's cysts , Rathke's cleft cysts groups of epithelial cells forming small colloid-filled cysts in the pars intermedia of the pituitary gland; they are vestiges of Rathke's pouch and are closely related to craniopharyngiomas.

retention cyst  one caused by blockage of the excretory duct of a gland, so that glandular secretions are retained.

sarcosporidian cyst  sarcocyst (2).

sebaceous cyst  a retention cyst of a sebaceous gland, containing cheesy yellow material, usually on the face, neck, scalp, or trunk.

solitary bone cyst  a pathologic bone space in the metaphyses of long bones of growing children; it may be either empty or filled with fluid and have a delicate connective tissue lining.

sterile cyst  a true hydatid cyst that fails to produce brood capsules.

subchondral cyst  a bone cyst within the fused epiphysis beneath the articular plate.

sublingual cyst  ranula.

tarry cyst 

1. one resulting from hemorrhage into a corpus luteum.

2. a bloody cyst resulting from endometriosis.

tarsal cyst  chalazion.

theca-lutein cyst  a cyst of the ovary in which the cystic cavity is lined with theca interna cells.

unicameral bone cyst  solitary bone c.

wolffian cyst  a cyst of the broad ligament developed from vestiges of the mesonephros.

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meibomian cyst.

See chalazion.

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cyst [sist]

1. bladder.

2. an abnormal closed epithelium-lined sac in the body that contains a liquid or semisolid substance. Most are harmless, but they should be removed when possible because 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.

3. a stage in the life cycle of certain parasites, during which they are enveloped in a protective wall.

adventitious cyst pseudocyst (def. 1).

alveolar c's dilatations of pulmonary alveoli, which may fuse by breakdown of their septa to form large air cysts (pneumatoceles).

arachnoid cyst a fluid-filled cyst between the layers of the leptomeninges, lined with arachnoid membrane, usually in the sylvian fissure.

Baker cyst a swelling on the back of the knee, due to escape of synovial fluid that has become enclosed in a sac of membrane.

Bartholin cyst a mucus-filled cyst of a Bartholin gland, usually developing as a consequence of an obstruction of the duct by trauma, infection, epithelial hyperplasia, or congenital atresia or narrowing.

Blessig c's cystic spaces formed at the periphery of the retina.

blue dome cyst

1. a benign retention cyst of the breast that shows a pale blue color. See also cystic disease of breast.

2. a cyst due to endometriosis, found in healed wounds such as those of an episiotomy or an incision for a cesarean section; it is usually found in the vaginal fornix or on the cervix.

Boyer cyst an enlargement of the subhyoid bursa.

branchial cyst (branchiogenic cyst) (branchiogenous cyst) see branchial cyst.

bronchogenic cyst a congenital cyst, usually in the mediastinum or lung, arising from anomalous budding during formation of the tracheobronchial tree, lined with bronchial epithelium that may contain secretory elements.

chocolate cyst one filled with hemosiderin, causing a dark color, following local hemorrhage, such as may occur in the ovary in ovarian endometriosis.

choledochal cyst a congenital cystic dilatation of the common bile duct, which may cause pain in the right upper quadrant, jaundice, fever, or vomiting, or be asymptomatic.

daughter cyst a small parasitic cyst developed from the walls of a larger cyst.

dentigerous cyst an odontogenic cyst surrounding the crown of a tooth, originating after the crown is completely formed.

dermoid cyst see dermoid cyst.

duplication cyst a congenital cystic malformation of the alimentary tract, consisting of a duplication of the segment to which it is adjacent, occurring anywhere from the mouth to the anus but most frequently affecting the ileum and esophagus.

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.

enteric cyst (enterogenous cyst) a cyst of the intestine arising or developing from some fold or pouch along the intestinal tract. Called also enterocyst and enterocystoma.

epidermal cyst (epidermoid cyst) an intradermal or subcutaneous cyst containing keratinizing squamous epithelium; it arises from occluded hair follicles. Called also wen.

epidermal inclusion cyst a type of epidermal cyst occurring on the head, neck, or trunk, formed by keratinizing squamous epithelium with a granular layer.

epithelial cyst

1. any cyst lined by keratinizing stratified squamous epithelium, found most often in the skin.

2. epidermal cyst.

exudation cyst a cyst formed by the slow seepage of an exudate into a closed cavity.

false cyst pseudocyst (def. 1).

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.

hydatid cyst the larval stage of the tapeworms Echinococcus granulosis and E. multilocularis; each one contains daughter cysts that have many scoleces (mouths). See also hydatid disease. Called also echinococcus cyst and hydatid.

inclusion cyst one formed by the inclusion of a small portion of epithelium or mesothelium within connective tissue along a line of fusion of embryonic processes; several types are found in the oral and nasal regions.

keratinizing 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 or rancid.

meibomian cyst chalazion.

mucus retention cyst a mucus-containing retention cyst caused by blockage of a salivary gland duct.

multilocular cyst

1. a cyst containing several loculi or spaces.

2. a hydatid cyst with many small irregular cavities that may contain scoleces but generally little fluid.

3. a thick-walled cyst in the kidney, found in clusters and usually unilaterally. In children it contains blastema and may develop into a Wilms tumor.

myxoid cyst a nodular lesion usually overlying a distal interphalangeal finger joint in the dorsolateral or dorsomesial position, consisting of focal mucinous degeneration of the collagen of the dermis; not a true cyst, lacking an epithelial wall, it does not communicate with the underlying synovial space.

Naboth's c's (nabothian c's) cysts that occur when mucus-producing glands in the columnar epithelium of the uterine cervix become covered over by squamous epithelium resulting from metaplasia; they are usually found in the transformation zone of the cervix. Called also Naboth's or nabothian follicles.

nasoalveolar cyst (nasolabial cyst) a fissural cyst arising outside the bones at the junction of the globular portion of the medial nasal process, lateral nasal process, and maxillary process.

odontogenic cyst one derived from epithelium, usually containing fluid or semisolid material, which develops during various stages of odontogenesis; nearly always enclosed within bone.

parasitic cyst one forming around larval parasites (tapeworms, amebas, trichinae), such as a hydatid cyst.

periapical cyst a periodontal cyst involving the apex of an erupted tooth.

perineurial cyst an outpouching of the perineurial space on the extradural portion of the posterior sacral or coccygeal nerve roots at the junction of the root and ganglion; it may cause low back pain and sciatica.

periodontal cyst one in the periodontal ligament and adjacent structures, usually at the apex of the tooth (periapical cyst).

pilar cyst a type of epidermal cyst, almost always found on the scalp, arising from the outer root sheath of the hair follicle.

pilonidal cyst see pilonidal cyst.

radicular cyst an epithelium-lined sac at the apex of a tooth.

Rathke's c's (Rathke's cleft c's) groups of epithelial cells forming small colloid-filled cysts in the pars intermedia of the pituitary gland; they are vestiges of Rathke's pouch and are closely related to craniopharyngiomas.

retention cyst a tumorlike accumulation of a secretion formed when the outlet of a secreting gland is obstructed. These cysts may develop in any of the secretory glands, such as the breast, pancreas, kidney, salivary or sebaceous glands, or mucous membranes.

sarcosporidian cyst sarcocyst (def. 2).

sebaceous cyst see sebaceous cyst.

solitary bone cyst a pathologic bone space in the metaphyses of long bones of growing children; it may be either empty or filled with fluid and have a delicate connective tissue lining.

subchondral cyst a bone cyst within the fused epiphysis beneath the articular plate.

tarry cyst

1. one resulting from hemorrhage into a corpus luteum.

2. a bloody cyst resulting from endometriosis.

theca-lutein cyst a cyst of the ovary in which the cystic cavity is lined with theca cells.

traumatic bone cyst a cavity (not a true cyst) formed in bone, particularly the mandible, in response to trauma. The hematoma precipitated by trauma is resorbed but bone is not replaced; the space formed is usually empty and lacks an epithelial lining.

unicameral bone cyst solitary bone cyst.

wolffian cyst a cyst of the broad ligament developed from vestiges of the mesonephros.

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cyst

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.

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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

see chalazion.

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

see morgagni's hydatid.

nabothian cyst

see cervical cyst (above).

orbital cyst

see mucocele.

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.

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meibomian

named after H. Meibom, a German anatomist.

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meibomian adenoma

commonest canine peri-ocular neoplasm.

meibomian cyst

see chalazion.

meibomian gland

see meibomian gland.

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chalazion 

A chronic inflammatory lipogranuloma due to retention of the secretion (such as blocked ducts) of a meibomian gland in the tarsus of an eyelid. It is characterized by a gradual painless swelling of the gland without marked inflammatory signs and sometimes astigmatism which is induced by the cyst pressing on the cornea (Fig. C5). Small chalazia may disappear spontaneously but large ones usually have to be incised and curetted (i.e. removal of the pus with a scraper) through a tarsal incision. Resolution may also occur after local injection of a corticosteroid drug (e.g. dexamethasone or triamcinolone). Syn. meibomian cyst (although it is not a true cyst because its walls are made of granulomatous tissue and not lined with epithelium). See internal hordeolum.

Fig. C5 Upper eyelid chalazion

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meibomian cyst

Chalazian, tarsal cyst Ophthalmology Inflammation of the sebaceous gland of the eyelid