Pathologic Correlation Study of Microwave Coagulation Therapy for Hepatic Malignancies Using a Three-Ring Probe

Microwave coagulation therapy (MCT) for the ablation of unresectable hepatic malignancies is a promising alternative to radiofrequency and cryoablation techniques. There are few data on the clinical effectiveness of MCT. In vivo pathologic evaluation of ablated tumor tissue is not well described for the three-ring microwave probe. The study design was a prospective trial enrolling patients with resectable hepatic malignancies. Lesions underwent in vivo MCT with the three-ring probe prior to liver resection. Gross and histologic evaluations of the tumor were performed, including nicotinamide adenine dinucleotide (NADH) vital staining. A total of nine patients with metastatic colon cancer were enrolled and had NADH stains performed of their pathologic specimens. The median size of the metastasis being ablated was 3.5 cm (range, 1.5–12.3). Fifty-six percent of the tumors demonstrated evidence of spontaneous coagulative necrosis on immediate histologic examination. The median dimensions of the ablation zones were 5 cm (range, 3–7) × 4.5 cm (range, 2.5–5.2) × 4.2 cm (range, 2–5) with a 5-min ablation at 60 W. The median ablation volume was 50.6 cm³ (range, 9–78). NADH vital staining was performed of the ablation zones with 100% absence of staining in the tumor tissue and in benign hepatic parenchyma, which is consistent with irreversible cellular damage. In conclusion, in vivo MCT of hepatic malignancies with the three-ring probe produces nonviable tumor cells after a 5-min ablation. The ablation time is significantly shorter than other available ablative techniques. Immediate histologic exam produces some evidence of coagulative necrosis. Further study of this promising technology is warranted.