Sudden enlargement of leiomyosarcoma is not necessarily malignant, but may be related to the increase of estrogen level. 1. Malignant change: if the fibroid has malignant change, that is, sarcomatoid change, it will cause the fibroid to increase rapidly in size in a short time, but the probability of this malignant change is very low. 2. Elevated estrogen level: if female body secretes a large amount of estrogen, or after supplementing estrogen-containing drugs by herself, the uterine fibroids will stimulate the growth of fibroids due to the distribution of estrogen receptor in the fibroids. For patients who are found to have a sudden increase in the size of uterine fibroids, it is recommended that they go to the gynecology department of regular hospitals to improve the pelvic MRI and other related examinations, so as to clarify the cause of the disease and then actively treat it under the guidance of doctors.