Medullary thyroid carcinoma has characteristics of ultrasound images compared with papillary carcinoma. Depending on the size of the tumor, ultrasound images of medullary thyroid carcinoma less than 1 cm in diameter are similar to those of tiny papillary carcinoma, with hypoechoic, poorly defined borders, irregular morphology, accompanied by calcification, and due to the malignant tumor acquiring nutritional requirements, it is mostly spherical in shape with large longitudinal and transverse comparisons. However, when the tumor diameter is larger than 1 cm, the image of medullary thyroid carcinoma mostly shows ovoid shape, regular boundary, with coarse calcification, and easy to occur lymph node metastasis.