Ultrasound-Guided Laser Ablation Using Multidirectional-Firing Fiber for Papillary Thyroid Carcinoma: An Ex Vivo Study with Evaluation of Tumor Cell Viability

Objective: The objective of this study was to evaluate the viability of tumor cells after laser ablation for papillary thyroid carcinoma and to determine if the laser ablation procedure using multidirectional-firing fiber had a therapeutic effect. Background data: Many noninvasive techniques have been introduced for the treatment of thyroid cancer. Among them, the laser ablation technique has been proven its therapeutic effect for large benign thyroid nodules. Materials and methods: Three patients who were diagnosed with papillary thyroid carcinoma using fine-needle aspiration cytology were enrolled. All of the selected tumors were >2 cm in size and there was no case of extrathyroidal extension. A laser fiber was inserted into the tumor by means of ultrasound guidance and ablation was performed for 3 min at 7 W of output power. The specimens were stained using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide (NADH), and were evaluated by a pathologist. Results: The specimen showed three clearly distinct zones: zone 1, carbonized zone; zone 2, coagulated zone; and zone 3, normal thyroid tissue. No remaining thyroid tissue was visible in zone 1 after staining, because of complete necrosis of the tumor cells. Although thyroid tissue remained in zone 2, no viable tumor cells were detected using NADH staining. Conclusions: It was found that laser ablation using multidirectional-firing fiber could be an effective treatment technique for papillary thyroid carcinoma. This technique enables not only direct cancer treatment with cell necrosis but also the securement of a tumor safety margin in a similar manner to surgery.