| odontogenic cyst, calcifying | A mixed radiolucent-radiopaque lesion of the jaws with features of both a cyst and a solid neoplasm. It is characterised microscopically by an epithelial lining showing a palisaded layer of columnar basal cells, presence of ghost cell keratinization, dentinoid, and calcification. (12 Dec 1998) |
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| oil cyst | A cyst resulting from loss of the epithelial lining of a sebaceous, dermoid, or lacteal cyst, or from the subcutaneous injection of oil or fat material. (05 Mar 2000) |
| omphalomesenteric cyst | Cystic lesion found within the umbilical cord, presumed to develop from remnants of the omphalomesenteric duct early in gestation. May be found on antenatal ultrasound. Synonym: omphalomesenteric duct cyst. (05 Mar 2000) |
| omphalomesenteric duct cyst | Cystic lesion found within the umbilical cord, presumed to develop from remnants of the omphalomesenteric duct early in gestation. May be found on antenatal ultrasound. Synonym: omphalomesenteric duct cyst. (05 Mar 2000) |
| oophoritic cyst | <gynaecology> The ovary will form a fluid filled cyst on the surface of the ovary each month after an egg is released from the ovary during normal ovulation. Larger cysts can cause pain and bleeding (rupture). (27 Sep 1997) |
| osseous hydatid cyst | A morphological form of hydatid cyst caused by Echinococcus granulosus, and found in the long bones or the pelvic arch of humans if the embryo is filtered out in bony tissue; in this site no limiting membrane forms and the cyst grows in an uncontrolled fashion, producing cancellous structures and inducing fracture, followed by spread to new sites. (05 Mar 2000) |
| ovarian cyst | <gynaecology> The ovary will form a fluid filled cyst on the surface of the ovary each month after an egg is released from the ovary during normal ovulation. Larger cysts can cause pain and bleeding (rupture). (27 Sep 1997) |
| ovary, dermoid cyst of the | Tumour that develops from a totipotential germ cell (a primary oocyte) retained within the egg sac (ovary). Being totipotential, that cell can give rise to all orders of cells necessary to form mature tissues and often recognizable structures such as hair, bone and sebaceous (oily) material, neural tissue and teeth. Dermoid cysts may occur at any age but the prime age of detection is in the childbearing years. The average age is 30. Up to 15% of women with ovarian teratomas have them in both ovaries. Dermoid cysts can range in size from a centimeter (less than a half inch) up to 45 cm (17 inches) in diameter. They can cause the ovary to twist (torsion) and imperil its blood supply. Although the large majority (about 98%) of ovarian teratomas are benign, the remaining fraction (about 2%) becomes cancerous (malignant). The larger the dermoid, the greater the risk of rupture with spillage of the greasy contents which can create problems with adhesions, pain etc. Removal is usually the treatment of choice by laparotomy (surgery) or laparoscopy (with a scope). Dermoid cysts of the ovary are also called simply dermoids or ovarian teratomas. (12 Dec 1998) |
| Tarlov's cyst | A perineural cyst found in the proximal radicles of the lower spinal cord; it is usually productive of symptoms. (05 Mar 2000) |
| tarry cyst | A cyst or collection of old blood having a tarry or black, sticky appearance; usually due to endometriosis. (05 Mar 2000) |
| tarsal cyst | Also called a Meibomian cyst or a chalazian. A tarsal cyst is an inflammation of the oil gland of the eyelid. (12 Dec 1998) |
| teratomatous cyst | A cyst containing structures derived from all three of the primary germ layers of the embryo. (05 Mar 2000) |
| ear cyst | A sebaceous cyst that occurs most commonly in the ear canal. They are bulging sac-like collections of dead skin cells and fluid. These cysts can be quite painful and may block the canal causing hearing loss. Treatment may include warm wet compresses, antibiotics (if infected) and surgical removal in some cases. Most resolve spontaneously. (27 Sep 1997) |
| echinococcus cyst | A cyst formed in the liver, or, less frequently, elsewhere, by the larval stage of Echinococcus, chiefly in ruminants; two morphological forms caused by Echinococcus granulosus are found in humans: the unilocular hydatid cyst and the osseous hydatid cyst; a third form in humans is the alveolar hydatid cyst, caused by Echinococcus multilocularis. Synonym: echinococcus cyst, hydatid. (05 Mar 2000) |
| thyroglossal cyst | <anatomy, embryology> A thyroglossal cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyroglossal cyst is a result of incomplete closure of a segent of a tube-like structure (the thyroglossal duct) that is present, and normally closes, as the embryo develops. Synonym: thyrolingual cyst. (07 Mar 2000) |