The Pattern Of Cell Survival In The Pig Liver Following One Freeze-thaw Cryosurgery Cycle

BACKGROUND: It is well established that in cryosurgery some cells can survive one freeze thaw cycle and that surviving cells are found at the margin of the frozen lesion. Numerous techniques are being developed to ensure the survival of frozen cells to the margin of the frozen region. OBJECTIVE: We thought that it would be of fundamental interest to observe the pattern of cell survival in a liver treated with one freeze-thaw cycle. MATERIALS AND METHODS: We performed six ultrasound-guided single freeze-thaw cryosurgery procedures on the liver of four Landrace pigs, using two cryosurgery probes separated by 25 mm inserted in parallel. Treated organs were removed 24 hours after the cryosurgery and processed for histology with hematoxylin and eosin. The tissues were analyzed with a digital slice scanner. RESULTS: We found an unexpected pattern of cell survival; sheets of live cells, about 200 μm in width, that follow the network of interlobular connective tissue septae to a distance of several millimeter from the outer edge of the one freeze-thaw cycle cryosurgery treated lesion. The sheets of live cells surround lobule cores that have undergone complete coagulative necrosis. In addition, larger blood vessels, as far as 5 mm from the outer rim of the treated lesion, have a major and complex effect on cell survival with large areas of completely necrotic and completely alive cells intermixed. CONCLUSION: This study may have value as a baseline for developing new cryosurgery protocols designed to ablate cells to the margin of the frozen lesion.