Purpose
To correlate the ground-glass opacities induced by pulmonary radiofrequency (RF) ablation with pathomorphology of the ablation zone.
Material and methods
CT-guided pulmonary RF ablations (n = 9) of 10 primary (n = 2) or secondary (n = 8) lung tumors (mean diameter: 19 mm) in 8 patients were performed. Three days after RF ablation surgical resection was performed followed by pathologic examination. Specimens were evaluated macroscopically and histologically by Hematoxylin-Eosin (HE) staining. In addition terminal deoxy-nucleotidyl transferase-mediated nick end-labeling (TUNEL) and electron microscopic investigations were performed. The pathological extent of coagulation was correlated with ground-glass opacities on helical CT immediately after RF ablation.
Results
Pulmonary CT-guided RF ablations were technical successful in all cases. Due to DNA fragmentation as determined by TUNEL and the results from electron microscopy indicating apoptotic bodies we supposed a complete ablation in 9/10 (90%) tumors, though the specimens retained a pattern of intact cells in HE stained sections. A zone of interstitial hemorrhage occurred at the outer boundary of the ablation zone with few cells showing DNA fragmentation. This zone was surrounded by an edema with nearly complete absence of DNA fragmentation. Hemorrhagic rim and edema had a width up to 7 mm. The extent and shape of ground-glass opacities surrounding the tumor tissue correspond to a safety margin, hemorrhagic rim, and edema.
Conclusion
Thermally induced ground-glass opacities during CT-guided pulmonary RF ablation correlate to the extent of induced coagulation but may lead to an overestimation of complete coagulation. Based on our results we suggest that 7 mm of ground-glass opacities during ablation procedure should surround the tumor tissue.