Sudden enlargement of breasts is not necessarily caused by diseases. It may also be related to pubertal development, menstruation and pregnancy; in addition, external injuries, mastitis, breast hyperplasia and breast tumors and other diseases can also cause this disease. 1. Pubertal development: pubertal females are in the stage of rapid development, which will result in rapid enlargement of breasts and the first menstruation. 2. Menstruation: During menstruation, the hormone levels in the body change rapidly, and some women may experience breast enlargement. 3. Influence of pregnancy: During pregnancy, the hormones in the body will also change significantly, and sudden breast enlargement can also occur. 4. External damage: the patient’s breast is hit by external force, which can lead to specific tissue damage, and then appear congestion, swelling and pain and other symptoms. 5. Mastitis: This can lead to congestion, redness and swelling of the affected area, which in turn can lead to sudden enlargement of the breasts. 6. Mammary hyperplasia: With the enlargement of the mammary glands, the symptoms of sudden breast enlargement can also be manifested. 7. Breast tumor: either malignant or benign tumors can lead to breast enlargement or hard lumps. This phenomenon may also be related to other factors. It is recommended to consult a doctor as soon as possible for examination and diagnosis of this disease caused by pathological factors, and should follow the doctor’s instructions for treatment.