Pathomorphologic evaluation of pulmonary radiofrequency ablation: proof of cell death is characterized by DNA fragmentation and apoptotic bodies.
BACKGROUND
Radiofrequency (RF) ablation is an increasingly applied technique. Promising results of hepatic RF ablation raised expectations of its capabilities for treatment of primary and secondary lung tumors. Because of different thermal and electrical properties of lung tissue, compared with liver tissue, a simple analogy of tissue response is not possible. The authors aimed to evaluate the effectiveness of image-guided pulmonary RF ablation and to characterize pathomorphology of tissue response.


METHODS
RF ablations of 11 pulmonary malignancies in 9 patients were performed under computed tomography (CT)-guidance. Three days after RF ablation, surgical resection was performed followed by pathologic examination. Specimens were evaluated macroscopically, histologically by hematoxylin and eosin (H & E) staining, terminal deoxy-nucleotidyl transferase-mediated nick end-labeling (TUNEL), and electron microscopy.


RESULTS
Tumor tissues and adjacent lung tissues were characterized by double-strand fragmentation as determined by TUNEL. Ultrastructurally apoptotic bodies were found, indicating apoptotic cells. Criteria for tissue necrosis were not fulfilled by standard histological staining (H & E), showing preserved tissue architecture and only few microscopic cellular details suggestive of tumor regression. Because of DNA fragmentation, as determined by TUNEL and results from electron microscopy, the authors confirmed the tumor tissue to be completely ablated in 10 (90.9%) cases. However, in 2 cases, a safety margin was absent.


CONCLUSIONS
CT-guided pulmonary RF ablation of pulmonary malignancies is a locally effective treatment. Three days after RF ablation, tumor tissue seemed to be thermally fixed still showing characteristics of vital tumor tissue in standard histological staining; however the tissue proved to be in regression toward coagulative necrosis verified ultrastructurally and by TUNEL.
Clasen
Stephan
S
Department of Diagnostic Radiology, Eberhard-Karls-University of Tubingen, University Hospital, Tubingen, Germany. stephan.clasen@med.uni-tuebingen.de
Krober
Stefan-Martin
SM
Kosan
Bora
B
Aebert
Hermann
H
Fend
Falko
F
Bomches
Andrea
A
Claussen
Claus D
CD
Pereira
Philippe L
PL
D000328:Adult; D000368:Aged; D017209:Apoptosis; D017115:Catheter Ablation / Q000379:methods*; D016923:Cell Death; D053938:DNA Fragmentation; D005260:Female; D006801:Humans; D008168:Lung / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D025321:Surgery, Computer-Assisted; D015898:Tomography Scanners, X-Ray Computed; D016896:Treatment Outcome