Thyroid nodules are mostly asymptomatic, and are observed using benign ultrasound or cytology. Most of the benign nodules do not require treatment. Regular observation of thyroid nodules with ultrasound is commonly used. Only a few benign nodules need intervention due to some factors (e.g., neck discomfort, cosmetic problem, and patients’ desire). Nowadays, surgery has not been the only option considered. Nonsurgical treatments include thyroxine suppression therapy, percutaneous ethanol injection, thermal ablation, and radioactive iodine therapy, etc. Thermal ablation covers four types: microwave ablation (MWA), radiofrequency ablation (RFA), laser ablation (LA), and high intensity focused ultrasound (HIFU). Numerous studies have implied these modalities in the treatment of benign thyroid nodules, thus exploring their efficacy, and safety. They proved to be an advantageous option for benign nodules with less trauma, less operation time, less hospitalisation expenses, and higher quality of life. For papillary thyroid microcarcinoma (PTMC) measuring 1 cm or smaller, and for very low-risk thyroid cancer without lymph node or distant metastasis on imaging studies (e.g., for T1aN0M0 non-small cell lung cancer), active surveillance has already been recommended as a reasonable choice in selected patients. So far, the safety, and feasibility of active surveillance has been described by several international centres. Thermal ablation is becoming an alternative treatment in the debate for low-risk PTMC. 3-to 5-year follow up clinical observation studies mainly from China, Korea, and Italy have proved the efficacy and safety of thermal ablation.

However, there are still some challenges in the surgical management of thyroid nodules. Regular observation for thyroid nodules with benign cytology, and for PTMC has been widely accepted, yet the monitoring frequency is still discussed. Thermal ablation has been proven to be effective and safety, however, confusion has been caused by the heterogeneity among the three methods in benign or malignancy thyroid nodules. Besides, regrowth and retreatment has gradually been an area of renewed focus in benign nodules, as well as the factors associated with regrowth and retreatment. Although thermal ablation for PTMC has been practiced worldwide, we must regretfully recognise that no test can perfectly evaluate postoperative situations, especially for recurrence and lymph nodes metastasis.

The aim of this Special Issue is to collate original research articles highlighting updates on nonsurgical management of thyroid nodules. Review articles discussing the state of the art are also welcome.

Potential topics include but are not limited to the following:

• Thyroid nodule
• Papillary thyroid microcarcinoma
• Active surveillance
• Thermal ablation
• Laser ablation
• Radiofrequency ablation
• Microwave ablation