Thyroid 4a indicates a 5%-15% probability of malignancy of thyroid nodules. Thyroid nodules can be classified into grades 1-5 according to the probability of malignancy. Among them, grades 1-3 are basically benign tumors. If there are no obvious symptoms and the volume is small, you can observe them temporarily and review the ultrasound regularly. Grade 4 thyroid nodules indicate a certain probability of malignancy, which can also be divided into 4a, 4b and 4c. Grade 4a thyroid nodules have a probability of malignancy of 5%-15%; 4b 15%-45%; and 4C 45%-75%. Therefore, if a woman has thyroid 4a, she should be reviewed regularly, and if necessary, fine needle aspiration of thyroid nodule tissue for pathological examination is required to make a clear diagnosis.