Purpose
For the majority of the surgical procedures, pathologist finding is a golden standard of the cure assessment, but isn't of that for the liver tumour radiofrequency ablation (RFA). The reasons of often false core-needle biopsy results after RFA were studied in the paper.
Material and methods
The histologic changes in RFA zones produced by cool-tip Radionic RFA system were studied in a) the animal model (3 rats - immediately, 1 day and 7 days after RFA), b) two liver specimens obtained and treated with RFA immediately after resection and c) four liver specimens excised 0.5, 1.5, 3.0 and 6.0 months after percutaneous RFA procedures. The standard light microscopy with H&E staining as well as the electron microscopy was performed. The geometry of the suspected of incompleteness RFA zone also was studied.
Results
Histologic evolution of RFA zone: The standard light microscopy (H&E staining) fails to reveal any changes in tissue immediately after RFA, while the electron microscopy demonstrates membranous structure damage (above all, mitochondrial destruction). One week later, the cells are still distinguished, thought the dilated sinusoids and thick inflammatory infiltration are evident. Two weeks after the procedure the cellular boundaries appear indistinct and the focal coagulative necrosis is present. Four weeks after RFA the coagulative necrosis replaces the treated tissue at the whole extent. Spatial considerations: The outer surface of a 3.0 cm in diameter RFA zone contains 1487 sites for obtaining the tissue by 16G core needle. Hence, the poorly imaged portion of the tumor during RFA procedure (suspected of incomplete RFA) is of the poor imaging for core-needle biopsy.
Conclusion
The results of core-needle biopsy after RFA are insecure due to the delayed light microscopy presentation of the coagulative necrosis and the high heterogeneity of the RFA zone suspected of residual or recurrent tumor. The core-needle biopsy is of limited usage for liver tumour RFA completeness assessment, leaving the priority to the imaging techniques.