Pathologic assessment of radiofrequency ablation of pulmonary metastases.

PURPOSE: To evaluate pathologically the effectiveness of radiofrequency (RF) ablation in the treatment of pulmonary metastases. MATERIALS AND METHODS: Patients with multiple pulmonary metastases scheduled for surgical resection were prospectively enrolled. Patients underwent RF ablation of one percutaneously accessible tumor and within 2-4 weeks underwent surgical resection of the ablated tumor and any additional lesions. Resected tumors all were assessed by routine light microscopy, and selected tumors were assessed by immunohistochemistry with MIB1 and proliferative cell nuclear antigen (PCNA). Relationship of ablation zone to the tumor and viability of the ablated tumors were assessed. RESULTS: Nine patients (four men and five women) 46-76 years of age were included in the study. Four patients had metastatic colorectal carcinoma, and five patients had metastases from soft tissue sarcomas. Ablated tumors ranged from 1.0-3.0 cm in diameter. Each target lesion was completely encompassed by the ablation zone. All tumor tissue within the ablation zone showed characteristic changes of coagulative necrosis with hematoxylin and eosin staining. Tumors showed preservation of MIB1 staining but loss of PCNA protein staining. RF ablation resulted in complete coagulative necrosis of all the pulmonary metastases treated in the study. CONCLUSIONS: Although this series is small, it provides histologic support for RF ablation as an effective treatment for selected pulmonary metastases.