Breast swelling and pain before menstruation after teratoma surgery may not be directly related to the surgery, and is usually caused by increased estrogen level, breast nodules, breast cysts and other reasons. 1. Increased level of estrogen: the level of estrogen in the patient’s body usually rises gradually before menstruation, and estrogen will stimulate the breast tissue, thus leading to physiological swelling and pain in the breast, which usually disappears gradually after menstruation. 2. Mammary gland hyperplasia: Mammary gland hyperplasia is usually caused by endocrine disorders, or may be caused by improper diet, improper work and rest, etc. When the mammary gland hyperplasia may lead to breast swelling and pain symptoms. 3. Breast cysts: Breast cysts are usually caused by the obstruction of the milk ducts due to the poor structure of the mammary glands, and if the patient suffers from breast cysts, it may cause the symptoms of breast swelling and pain. There are many reasons for breast swelling and pain before menstruation, and it is recommended that patients consult regular hospitals for a clear diagnosis before treatment.