cyst

/sist/, n.

1. Pathol. a closed, bladderlike sac formed in animal tissues, containing fluid or semifluid matter.

2. a bladder, sac, or vesicle.

3. Bot., Mycol.

a. a sporelike cell with a resistant, protective wall.

b. a cell or cavity enclosing reproductive bodies.

4. Zool.

a. a sac, usually spherical, surrounding an animal that has passed into a dormant condition.

b. such a sac plus the contained animal.

c. a capsule or resistant covering.

[1705-15; < NL cystis < Gk kýstis bag, pouch, the bladder; akin to kyma CYMA]

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Enclosed sac within body tissues.

It has a distinct membrane and generally contains liquid. Most cysts are benign, but several kinds may be malignant or precancerous. Benign cysts often press on nearby organs and require removal. Formed by overproduction of epithelium (surface tissue of anatomical structures), cysts may become detached from surrounding structures and move freely. They can contain natural secretions, abnormal breakdown products, or, in infections, bacteria, larval parasites, and microbial products. Some organs, including the kidney, liver, and breast, can become filled with cysts as a result of cystic diseases that may be dangerous or may hide more serious diseases. See also tumour.

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▪ neoplasm

      in biology, enclosed sac within body tissues, having a distinct membrane and generally containing a liquid material. In the life cycle of certain parasitic worms, a cyst develops around the larval form within the muscle tissue of the host animal.

      Although the majority of cysts are benign, several varieties may be malignant or precancerous. Benign cysts often require removal because they interfere with surrounding organs. Cysts form from a proliferation of epithelium, the tissue making up the skin and the linings of the blood vessels and body cavities, and may become detached from surrounding structures so that they move freely. The material inside can consist of natural body secretions, abnormal products from the breakdown of natural secretions and structural proteins, or, in case of infection, bacteria, larval parasites, and microbial products.

      Several organs, including the kidney, liver, and breast (mammary gland), are particularly susceptible to cyst formation and may become filled with numerous cysts of various sizes. In some cases, these cystic diseases are themselves dangerous, or they may obscure more serious, underlying diseases.

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