Cryotherapy of the liver: A histological review

Cryotherapy has been largely used in the past for palliation of unresectable liver tumors, but high local recurrence rates and peculiar systemic complications have determined its progressive abandonment. This review analyzes the histological changes produced to provide the basis for the local recurrences. A detailed literature search was performed on studies focusing on liver cryotherapy. Included were only those that described the histological characteristics in detail. A total of 22 studies were found, one clinical and the others in-vivo animal studies. Similar to other ablative techniques, cryotherapy produces a lesion which is composed by a central zone of coagulative necrosis surrounded with a transitional inflammatory zone. The lesion’s dimensions and morphology are influenced by numerous factors including the probe temperature, diameter, the duration of freezing time, fast cooling rate, slow thawing rate, the number of freezing cycles and the inflow occlusion (Pringle maneuver). The temporal evolution is consistent across studies and leads to a progressive inflammatory invasion of the necrosis with definitive fibrotic substitution. Lesions obtained after cryotherapy seem similar and behave as those obtained after other techniques of liver ablation. However, controversial areas still exist and include the optimum number of freeze thaw cycles, the place of inflow occlusion, the potential corrupting effects of intra-lesional or proximal blood vessels on ablation morphology. The influence of these factors on the local recurrences are still not fully understood.