[Cryobiology and pathologic lesions induced by freezing-thawing processes in prostatic tissue. Second part]

Cryosurgery is an emerging technology consisting on controlled freezing of tissues. Good results, maintained in the long-term, have been referred in the treatment of prostate adenocarcinoma. A role as possible substitute of partial nephrectomy in the treatment of renal adenocarcinomas smaller than 4-5 cm is under research. There is no discussion that freezing destroys cellular machinery and triggers several events the final result of which is cell death by necrosis and apoptosis. The decrease of temperature makes extracellular liquid crystallize and creates a hyperosmotic environment, which induces water to go out of the cell producing intracellular dehydration. Intracellular ice is created with fast freezing speeds being attributed the most destructive effect on biological tissues with irreparable damage. In blood vessels, it directly induces endothelial cell death and mechanical lesions of the endothelium; the consequence is the formation of thrombi that obstruct the lumen of the vessel. In the post-thawing phase there is an increase in free radicals formation and neutrophil activity, which induces cellular membrane lipids peroxidation and new endothelium lesions. Tissue destruction is determined by: minimal temperature achieved, freezing speeds, freezing phase duration, number of freezing-thawing cycles provided, and distance to the freezing focus. As we move away from the freezing focus cells are affected in different ways, and there are several mechanisms proposed to explain the lethal action induced by temperatures higher than--40 degrees C. In our series pathologic findings were: necrosis, hemorrhagic areas either developed or not, fibrosis, hyalinization and increases in the relative number of hematic capillaries, microscopic calcifications, basal cells hyperplasia, and transitional or squamous metaplasia. Residual cancer is localized in the areas less affected by freezing. It should be emphasize the scarce morbimortality associated with the procedure. It does not require ICU admission or blood transfusions, no cerebral vascular accidents (CVA) or heart events have been described, and mortality is null, so that it is feasible in high surgical risk patients and without age limit.