Small thyroid cancers, generally referred to as microscopic papillary thyroid cancers. Since the biology of this type of cancer is inert and the vast majority of lesions can remain unchanged for a long time without intervention and will not affect survival, more and more guidelines and clinical experts suggest that this type of small cancers can be managed by follow-up observation without excessive intervention. Micro papillary thyroid carcinoma is generally defined as small carcinoma with the largest radial direction not exceeding 1.0 cm (click →_→ Micro papillary thyroid carcinoma). Due to the high sensitivity and high resolution of ultrasound examination, experienced ultrasonographers have no problem at all in diagnosing small cancers of several millimeters in size. Therefore, ultrasonography has become the best means to follow up the diagnosis of micro papillary thyroid cancer. However, not all small cancers smaller than 1.0 cm are suitable for follow-up observation. Experts and most guidelines recommend that these small carcinomas should no longer be followed up and should be surgically treated once the following conditions are detected on ultrasound: Invasion of the thyroid peritoneum. Invasion of the trachea. Multiple small carcinomas in the thyroid gland. Metastases in the surrounding lymph nodes. Therefore, after the sonographer has determined the nature of the thyroid nodule, the most critical thing to determine during follow-up is whether the nodule has perineural invasion, tracheal invasion, lymph node metastasis, or whether it is multiple. This important information is provided to the surgeon in order to help the clinician make a reasonable clinical decision.