Although fibroids are benign diseases, there are a few cases in which they may become malignant. If malignancy occurs, it is called fibrosarcoma and is definitely a malignant tumor. Therefore, if a fibroid tumor suddenly grows, becomes irregular in shape or becomes particularly hard, it is necessary to go to the hospital for an early examination to rule out the possibility of malignancy. If the tumor is very large, adjuvant radiotherapy and chemotherapy will be required after surgery.