4a is actually a classification within the BI-RADS classification of breast ultrasound. The BI-RADS classification can be divided into 6 levels: 0, 1, 2, 3, 4, 5, of which 4 is divided into 3 subclasses: 4a, 4b, 4c. 4a refers to The benign tendency is relatively large, and the malignancy rate is only 3%-30% in grade 4a. Some indeterminate fibroids, intraductal lesions, and undiagnosed suspected inflammatory mammary lesions can be classified as 4a. 4a is more likely to be benign, but malignancy cannot be ruled out. For nodules in category 4a, there is no need to be alarmed, as further diagnostic aids such as puncture can be performed to confirm the diagnosis. Although benign is more likely, malignancy cannot be ruled out.