Breast enlargement pus after a few days of medication may be caused by breast trauma, bacterial infection, tumor lesions and other reasons. 1. Breast trauma: If the breast of a patient with breast hyperplasia is traumatized, the formation of an inflammatory mass in the local tissues or the appearance of hematoma inside the breast may lead to purulent changes. 2. Bacterial infection: if there is an infectious disease such as mastitis, bacteria and viruses invade the breast tissue, which can also lead to suppurative changes in the breast. 3. Tumor lesions: mostly seen in patients with large tumor tissues, due to the rapid development of the lesion, ischemia and necrosis of the internal tissues of the lesion can occur, resulting in the formation of internal breast abscesses. It is recommended that patients should go to the breast surgery department of the hospital in time, through ultrasound, molybdenum target, blood routine, pathology and other examination items, to diagnose the type of lesion, and take corresponding treatment measures under the guidance of doctors.