Thyroid 4C generally refers to the TIRADS-4C grade in the ultrasound malignancy risk stratification of thyroid nodules. It is recommended to carry out puncture examination to clarify the benignness or malignancy of the nodule, and then carry out surgery if it is malignant, and the benign nodule usually does not need surgery, and follow-up observation is sufficient. TIRADS-4 grade suggests that the nodule is suspected of malignancy, including 4A, 4B and 4C, which are low, moderate and highly suspected of malignancy, respectively. Among them, the malignancy rate of the nodule in TIRADS-4C is 50% to 90%, and it is recommended to carry out ultrasound-guided fine-needle aspiration biopsy (FNA) to clarify the benignity or malignancy of the nodule. If the nodule is malignant, surgical treatment is usually recommended to remove the lesion; if the aspiration biopsy clarifies that the nodule is benign, surgical treatment may not be necessary, and regular follow-up observation will be performed. If thyroid 4c is detected, prompt medical attention is recommended.