High-resolution ultrasonography is the method of choice for the evaluation of thyroid nodules. Ultrasound of the neck should be performed in cases of suspected thyroid nodules on palpation or if they are suggested by X-ray, computed tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET). Ultrasound of the neck can confirm the presence of “thyroid nodules”, determine their size, number, location, texture (solid or cystic), shape, border, envelope, calcification, blood supply and relationship to surrounding tissues, and assess the presence and size, morphology and structural characteristics of lymph nodes in the neck area. Certain ultrasound signs can help in the differentiation of benign and malignant thyroid nodules. Almost all thyroid nodules with the following two types of ultrasound changes are benign: 1) purely cystic nodules; 2) nodules with multiple small vesicles occupying more than 50% of the nodule volume: 99.7% of nodules with spongy changes are benign. The following ultrasound signs suggest the possibility of thyroid cancer: 1) solid hypoechoic nodules; 2) rich blood supply in the nodules (in case of normal TSH); 3) irregular nodule shape and margin, halo absence; 4) microcalcifications, pinpoint diffuse distribution or clusters of calcifications; 5) nodules with aspect ratio >1; 6) abnormal ultrasound images of lymph nodes in the neck: e.g. round lymph nodes, irregular or blurred borders, uneven internal echogenicity. 6. Ultrasound image abnormalities of the lymph nodes in the neck, such as rounded lymph nodes, irregular or blurred borders, uneven internal echogenicity, internal calcification, indistinct corticomedullary demarcation, disappearance of lymph gates or cystic changes. If three or more of the above ultrasound signs are met, surgery is recommended. Ultrasound-guided fine-needle aspiration biopsy (FNAB) is the most sensitive and specific method to preoperatively assess the benignity of thyroid nodules and determine whether surgery is needed. Ultrasound-guided fine-needle aspiration biopsy + perforated cytology is recommended for all thyroid nodules >1 cm in diameter. For thyroid nodules that cannot be determined as benign or malignant by ultrasound-guided fine-needle aspiration biopsy, thyroid cancer molecular marker testing can be performed on the puncture specimen, such as the liquid thyroid cancer detection chip from AsuraGen, USA.