| adventitious cyst | 1. An accumulation of fluid in a cystlike loculus, but without an epithelial or other membranous lining. Synonym: adventitious cyst, false cyst. 2. A cyst whose wall is formed by a host cell and not by a parasite. 3. A mass of 50 or more Toxoplasma bradyzoites, found within a host cell, frequently in the brain; formerly called a pseudocyst, but now considered a true cyst enclosed in its own membrane within the host cell that may rupture to release particles that form new cysts, and apparently is infective to another vertebrate host. See: bradyzoite. Origin: pseudo-+ G. Kystis, bladder (05 Mar 2000) |
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| allantoic cyst | Cyst occurring in a persistent portion of the urachus, presenting as an extraperitoneal mass in the umbilical region. It is characterised by abdominal pain, and fever if infected. It may rupture, leading to peritonitis, or it may drain through the umbilicus. (12 Dec 1998) |
| alveolar hydatid cyst | A hydatid cyst of a multiloculate type, usually in the liver, caused by Echinococcus multilocularis, adults of which are in foxes; larvae (alveolar hydatid) are found chiefly in microtine rodents, but also among humans such as trappers and others handling pelts of infected foxes and other carnivores; growth is by exogenous budding and is not limited by an outer laminated membrane as in the hydatid cyst from E. Granulosus; necrosis, cavitation, contiguous spread, and death usually ensue. Synonym: multilocular hydatid cyst, multiloculate hydatid cyst. (05 Mar 2000) |
| aneurysmal bone cyst | <radiology> ABC, 10 - 30 yrs, 75% before skeletal maturity, sites: long bones; also, flat bones Findings: metaphyseal if unfused, metaepiphyseal after fusion, lytic, expansile, thin, continuous rim, thin internal bony strands (12 Dec 1998) |
| angioblastic cyst | Mesenchymal tissue capable of forming blood in the embryo. (05 Mar 2000) |
| apical periodontal cyst | An inflammatory odontogenic cyst derived histogenetically from Malassez' epithelial rests surrounding the root apex of a nonvital tooth. Synonym: periapical cyst, radicular cyst, root end cyst. (05 Mar 2000) |
| apoplectic cyst | A pseudocyst formed of extravasated blood as in a stroke. (05 Mar 2000) |
| arachnoid cyst | A fluid-filled cyst lined with arachnoid membrane, frequently situated near the lateral aspect of the fissure of Sylvius; usually congenital in origin. Synonym: leptomeningeal cyst. (05 Mar 2000) |
| baker cyst | <radiology> Bursal fluid collection between: medial head of gastrocnemius muscle and, semimembranosus tendon, associated with knee injury, may contain osteocartilaginous fragments (12 Dec 1998) |
| Baker's cyst | <rheumatology> A synovial cyst or pouch that occurs in the synovial lining of the knee. Presents in the popliteal fossa (are behind the knee). Synovial fluid escapes from the knee joint and into the cyst in individuals who suffer from degenerative and other joint disease. Typically these cysts are not painful unless swelling is extensive. Aspiration of the cyst is therapeutic only temporarily since recurrence is common. most disappear spontaneously after several years. Larger cysts can be removed surgically. Rupture of a Baker's cyst can present with painless and swelling to the calf. (27 Sep 1997) |
| Bartholin's cyst | A cyst arising from the major vestibular gland or its ducts. (05 Mar 2000) |
| benign ear cyst | A disorder where there are noncancerous lumps or growths within the ear canal or on the pinna of the ear (external ear). most lumps are sebaceous cysts but some are bony overgrowths known as exostoses (or osteomas). If large enough they may interfere with hearing. In this case surgical removal may be required. (27 Sep 1997) |
| bile cyst | <anatomy> A digestive organ which stores bile (produced in the liver), used in the digestion and absorption of fats in the duodenum. (27 Sep 1997) |
| blood cyst | A cyst containing blood or resulting from the encapsulation of a haematoma. Synonym: blood cyst, haematocele, haematocyst, sanguineous cyst. (05 Mar 2000) |
| blue dome cyst | Cyst in the breast filled with serum and/or blood. With time they look blue. (16 Dec 1997) |