The study aimed to compare the efficacy and safety of papillary thyroid microcarcinoma (PTMC) treated with microwave ablation(MWA) and surgery resection (SR), and to explore the tumor characteristics suitable for each treatment methods (such as with and without capsular invasion). The investigators organized 18 hospitals to participate in this multicenter study. Patients meeting following indications will be included in this study: 1. Biopsy pathology proved PTMC, but not high-risk subtype; 2. solitary mPTC, without US-detected gross extrathyroid extension; 3. no evidence of metastasis; 4 willing to participate in this study and perform regular follow-up. Patients themselves decide to receive MWA or SR for mPTC after medical consultation. Baseline characteristic including age, gender, thyroid function et al. will be collected. The treatment protocols of MWA and SR were according to the Chinese and international guidelines. The primary outcomes were the disease progression, including local tumor recurrence, lymph node metastasis, and distant metastasis. The secondary outcomes include thyroid function, complication rate, blood loss et al. Investigators will follow up enrolled patients and collect and upload data according to the trial. Treatment outcomes of tumor with and without US-detected capsular invasion was analyzes as subgroups.

The treatment protocols of MWA and SR were according to the Chinese and international guidelines. MWA need to ablate all tumors including at least 2mm safe margin except for tumors adjacent to thyroid capsule. SR basic protocol is lobectomy. All patients need to receive levothyroxine therapy to keep TSH lower than 0.5 mU/L. Patients in both groups underwent regular medical imaging and laboratory tests 1 month, 3-month, 6-month, 12-month, 18-month, 24-month and 36-month after treatment.

Inclusion Criteria:

• Biopsy pathology proved micropapillary thyroid carcinoma(mPTC), but not high-risk subtype
• Solitary mPTC, without US-detected gross extrathyroid extension
• No evidence of metastasis
• Willing to participate in this study and perform regular follow-up

Exclusion Criteria:

• Severe blood coagulation dysfunction (platelet count < 50x109/L cells or INR>1.5)
• Acute or severe chronic renal failure, pulmonary insufficiency or heart dysfunction
• Poor control of blood pressure(systolic pressure≥150mmHg or diastolic pressure≥95mmHg)
• Poor control of blood glucose(fasting glucose>10mmol/L)
• The opposite vocal cords dysfunction
• Diagnosed with other malignant tumors
• Pregnant and lactating women
• Other conditions that investigator believe are not appropriate to be enrolled