The probability of a thyroid 4a nodule with poorly defined borders being benign is about 90% to 98%. According to the guidance in the 2020 Chinese Guidelines for Ultrasound Malignancy Risk Stratification of Thyroid Nodules: C-TIRADS, the likelihood of malignancy for a TIRADS grade 4a nodule is 2% to 10%, so the probability of benignity is 90% to 98%. Thyroid nodule grade 4a is recommended to take further biopsy for pathological examination, if it is a benign nodule with small size and no obvious pressure symptoms, it can be followed up regularly for review, if it is suggestive of malignancy, it should be surgically removed in time. When TI-RADS grade 4a nodules are found, it is recommended to consult a regular physician in time and treat under the guidance of the doctor.