Calcified thyroid foci are different from those of tuberculosis, where calcified foci are generally the criterion for cure, whereas a significant proportion of thyroid nodules with calcification are malignant and some require surgery. Calcifications in thyroid nodules are diffusely dense calcifications, annular calcifications, coarse granular calcifications and mass-like calcifications according to their shape and distribution characteristics. According to rough statistics, more than 3/4 of hypoechoic nodules with dense multiple calcifications are thyroid carcinoma, the mechanism of which is unknown, probably due to calcium salt deposition after tumor cell metabolism or necrosis. It may be due to metabolism of tumor cells or calcium salt deposition after necrosis. Biopsy or surgery is required. 2. Calcification of thyroid cyst wall: Most of them are benign and occur due to calcium salt deposition in the cystic fluid. 3. Multiple coarse granular calcifications: Hypoechoic nodules with multiple coarse granular calcifications have a high possibility of malignancy and some of them are medullary carcinoma, especially those with lymph node metastasis should be considered as medullary carcinoma. Biopsy or surgery is needed. 4.Mass-like calcification: the whole nodule is like a stone, most of them are fibrotic calcification of thyroid nodules, which is benign and can be observed. Because the tissue is too hard, the biopsy needle sometimes cannot take the tissue. Cystic solid masses with calcification in the solid part are the same as hypoechoic nodules with calcification. Especially if there is a papillary projection of the solid part within the cyst, calcification of the solid part is equally considered as a malignant possibility.