 Papillary thyroid microcarcinoma PTMC is a common tumor in Hong Kong. Early immediate surgery has traditionally been recommended. However, given its excellent prognosis, some have recommended Active Surveillance AS as an alternative. AS involves monitoring the patients who have PTMC until the tumor progresses. On the other hand, a new technology of ablation has been developing to be an alternative treatment for thyroid nodules comparing with traditional surgery, named High intensity focused ultrasound HIFU. In our previous study, HIFU is proved in shrinking the size of target site by 6 months gradually and effectively. 