Calcification of thyroid tumor refers to the phenomenon of calcium deposition within the thyroid tumor, which is manifested as various forms of strong echogenicity on ultrasound images and various forms of high-density shadows on CT images. Calcification of thyroid tumor is further divided into coarse calcification and microcalcification. The diameter of calcified nodules in ultrasound examination is greater than 2mm, and the ultrasound shows calcified foci with strong light clusters, lamellae, arcs or other irregular shapes. Microcalcifications are calcifications in nodules less than 2 mm, which appear on ultrasound as pinpoint-like or granule-like dots or sand grains. Microcalcifications occur mostly in malignant nodules. In general, coarse calcifications are more common in benign nodules and microcalcifications are more common in malignant nodules.