n. a bladder-like cyst formed in various human tissues following the growth of the larval stage of an Echinococcus tapeworm. E. granulosus produces a single large fluid-filled cyst, called unilocular hydatid, which gives rise internally to smaller daughter cysts. The entire hydatid is bound by a fibrous capsule. E. multilocularis forms aggregates of many smaller cysts with a jelly-like matrix, called an alveolar hydatid, and enlarges by budding off external daughter cysts. Alveolar hydatids are not delimited by fibrous capsules and produce malignant tumours, which invade and destroy human tissues. See also hydatid disease.
Subjects: Medicine and Health.