Ultrasound-Guided Percutaneous Laser Ablation of Papillary Thyroid Microcarcinoma: A Feasibility Study on Three Cases with Pathological and Immunohistochemical Evaluation

Background: Ultrasound-guided thermal laser ablation (LA) is a nonsurgical technique that has been proposed, but not fully assessed, for papillary thyroid microcarcinoma (PTMC) treatment. The objectives of this study were to evaluate the clinical feasibility of LA on PTMC as a primary treatment and to prove histologically the absence of residual viable tumor after LA procedure. Methods: Three patients with a Thy 6 diagnosis at fine-needle aspiration cytology with a single PTMC smaller than 10mm volunteered after full explanation of the protocol. At ultrasound examination, patients had no extrathyroid extension and no evidence of lymph node metastasis. Patients underwent percutaneous ultrasound-assisted LA of the PTMC in the operating room under general anesthesia. One 300m plane-cut optic fiber was inserted through the sheath of 21G Chiba needle, exposing 5mm of the nude fiber in direct contact with tumor tissue, and connected with a laser source operating at 1.064m with 3 W output power. Total energy delivery was 1800J. The surgeon directly started a standard total thyroidectomy. During surgical inspection, no remarkable laser sign was observed in the muscles, the perithyroidal tissues, or the recurrent laryngeal nerves. Results: Conventional histology showed destructured and carbonized tissue. Lack of vitality was demonstrated by complete loss of TTF1 and antimitochondria antibody expression in the whole ablated area and in the rim of normal tissue surrounding the tumor. BRAF V600E mutation was detected in cases 1 and 2. Furthermore, in cases 2 and 3, incidental papillary microfoci were found. A lymph node micrometastasis (200m) was observed in case 2. Conclusions: This study demonstrates that percutaneous LA is technically feasible for complete PTMC destruction. Now, LA may be useful in selected patients with PTMC, either when the surgeon or a patient refuses surgery, or when the patient is at high risk for an operation. LA may become a primary choice of treatment for PTMC only if future new knowledge would permit preoperative recognition of multifocality and lymph node metastasis.