The 4a in color ultrasound generally refers to the classification level, and the ultrasound classification of thyroid nodules and breast nodules is currently commonly used in color ultrasound classification. Color ultrasound nodules are classified as 4a, which refers to low risk of malignancy, that is, the risk of malignancy is less than 10%, but all of them also require puncture biopsy for pathological histology to confirm the diagnosis. Thyroid nodules TI-RADS classification is divided into a total of 1-6 categories, thyroid category 4a means the risk of malignancy is between 5%-10%, breast classification is divided into a total of 0-6 categories, its 4a category malignancy risk is between 3%-10%. The thyroid is classified according to the criteria, category 1 is normal, category 2 benign, category 3 possible benign nodules, category 4 suspicious malignant nodules, category 5 highly suspicious of malignancy, and category 6 pathological biopsy confirmed malignant lesions. Breast classification criteria, category 0 is incomplete information and needs to be re-evaluated in conjunction with other examinations, category 1 is no abnormality seen, category 2 is benign lesion, category 3 is highly probable benign, category 4 is suspicious malignant, category 5 is highly suspicious malignant, and category 6 is pathologically confirmed malignant lesion.