Thyroid nodule 4a with calcification may be dangerous and has some chance of malignancy and should be treated under medical supervision. Thyroid nodules are classified into 6 grades according to the TI-RADS classification, and common signs of malignancy include solid nodules, hypoechoicity, irregular margins, imbalance of aspect ratio, and tiny calcifications, etc. The chance of malignant lesions in thyroid nodule 4a is about 2-10%, and it is recommended to perform a fine-needle aspiration biopsy of the thyroid gland to clarify the benignness or malignancy of the nodule. If the pathology suggests benign, it is not dangerous and can be reviewed periodically. If the pathology suggests malignancy, it is more dangerous and requires early surgical treatment. Patients with thyroid 4a nodules are recommended to be treated under a doctor’s supervision.