Cryosurgery (also called cryotherapy) is the use of extreme cold to destroy cancer cells. Traditionally, it has been used to treat external tumors, such as those on the skin, but recently some physicians have begun using it as a treatment for tumors that occur inside the body. Cryosurgery for internal tumors is increasing as a result of developments in technology over the past several years.

For external tumors, liquid nitrogen (-196 degrees Celsius, -320.8 degrees Fahrenheit) is applied directly to the cancer cells with a cotton swab or spraying device. For internal tumors, liquid nitrogen is circulated through an instrument called a cryoprobe, which is placed in contact with the tumor. To guide the cryoprobe and to monitor the freezing of the cells, the physician uses ultrasound (computerized moving pictures of the body generated by high-frequency sound waves). By using ultrasound, physicians hope to spare nearby healthy tissue.

Cryosurgery often involves a cycle of treatments in which the tumor is frozen, allowed to thaw, and then refrozen.

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