That is, what about the gradual transformation of uterine fibroids into uterine sarcoma? There are 2 views: one is that there is no evidence of malignant transformation of fibroids. The National Institutes of Health (NIH, the most authoritative agency) believes that there is no evidence of fibroid malignancy. There is no evidence that uterine sarcoma is the transformation of uterine fibroids. Second, it is believed that fibroids have a 0.4-0.8% malignancy rate. This is mainly due to the fact that some of those diagnosed preoperatively as uterine fibroids, but postoperative pathology suggests uterine sarcoma.