Multiple bilateral breast nodules may be caused by breast cystic hyperplasia, plasma cell mastitis, local tumor and other diseases. 1. Breast cystic hyperplasia: when endocrine disorders, it is easy to lead to breast hyperplasia and incomplete degeneration, which in the long run will lead to multiple breast nodules and accompanied by breast swelling and pain. 2. Plasma cell mastitis: if the patient has the symptom of breast duct obstruction, it will easily cause the obstruction of milk or secretion discharge, resulting in the change of breast duct epithelial cells and the emergence of multiple breast nodules. 3. Local tumor: when suffering from fibroma or multiple lipomas of the breast and other diseases, it will easily lead to multiple breast nodules. Multiple bilateral breast nodules may also be caused by malignant tumors of the breast, etc. If you have multiple bilateral breast nodules, you should go to the hospital in time to get a clear picture of the cause of the disease, and then get the right treatment under the guidance of the doctor.