therapeutic technique in which localized freezing is used to remove or destroy diseased tissue. Rapid cooling of body tissues to a temperature of -60° C or lower causes ice crystals to form, disrupting cell structure and, ultimately, killing the cell. Freezing may also destroy tissues by triggering an immune response, releasing intracellular proteins that attract natural antibodies (antibody). These antibodies, in turn, destroy the diseased cells.

Various attempts to freeze tissue—using ice, liquid air, and solid or superchilled carbon dioxide—date to the 1850s, but the first efficient cryosurgical system applicable to internal tissues was developed by a U.S. neurosurgeon, Irving Cooper, in 1961. Cooper used liquid nitrogen to destroy brain tumours. Cryosurgery is now used in the removal of skin lesions, control of gynecologic and urologic tumours, lens extractions in ophthalmology, elimination of hemorrhoids, and other conditions involving diseased tissue.