GE Logiq E8, Toshiba Aplio 500, and Philips IU22 ultrasound diagnostic systems and high-frequency linear array probes (5–12 MHz) were used to assess the number, size, echogenicity, border, margin, shape, microcalcification, blood flow, and capsular invasion of the tumor. If the patient had multiple lesions, the largest one was selected as the observation object. The tumors were divided into three groups: the largest diameter <10 mm, 10–20 mm, and >20 mm. The blood flow of the tumor was graded by the Adler semiquantitative method,29 (link) according to the following criteria: Grade I: no obvious blood flow, indicating the absence of obvious blood flow signal inside the tumor; Grade II: small amount of blood flow, showing 1–2 punctate or short rod blood flow signals in the tumor; Grade III: moderate blood flow, showing 3–4 punctate blood flow signals or one long strip of blood flow signal in the tumor; and Grade IV: abundant blood flow, showing >5 punctate blood flow signals, >2 long strip blood flow signals, reticular blood flow signals, or dendritic blood flow signals. At ultrasound, when it was observed that the tumor was in contact with >25% of the adjacent thyroid capsule, or the thyroid capsule was disrupted by the tumor, or the soft tissue around the thyroid gland was invaded, it was defined as capsular invasion.6 (link),30 (link),31 (link)