The effects of radiofrequency ablation on the hepatic parenchyma: histological bases for tumor recurrences.

Background: This review examines histological modifications obtained after liver radiofrequency ablation (RFA).
Methods: A literature search has been undertaken for all pre-clinical and clinical studies involving RFA and in which ablation zones have been excised for a complete histological examination.
Results: Two main histological areas are present, a central zone of coagulative necrosis and a peripheral rim of congestion and extravasation. Both corresponded to specific microscopic characteristics that evolved over time and that are influenced by the proximity of patent vessels and the liver perfusion status. Viable cells are not present in the central zone but have been described in the ischemic peripheral rim where they survive the ischemia and inflammation process. These correspond in clinical studies to residual viable tumor cells that lead to failure of the procedure.
Conclusions: Histological changes following RFA are complex and interactions take place at both a cellular and tissue level. Changes in the peripheral zone must be considered in future studies in order to extend the volume of reliable tumor destruction and increase the effectiveness of the procedure.
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