Breast 4a refers to a commonly used way of grading breast nodules. It means that breast nodules reach BI-RADS grade 4 in the grading of ultrasound or mammography. If they reach grade 4a, it indicates that the breast nodules are relatively irregular, have some blood flow signal, have microcalcifications and other conditions that are suspected to have malignant changes on imaging. In clinical practice, usually BI-RADS grade 4 breast nodules are malignant in some cases, not all cases are malignant with such findings. In clinical practice, a biopsy of the breast lump should be further performed in breast surgery, and further frozen or paraffin pathological examination should be done to determine the nature of the lump and then treat it symptomatically.