Objective To investigate the MRI characteristics of low-grade endometrial stromal sarcoma (LGESS),and to improve the accuracy of the diagnosis.Methods The clinical and MRI data of 4 cases with LGESS confirmed by surgery and pathology were analyzed retrospectively.All cases underwent conventional MRI scans.Results All 4 cases had enlarged uterus in different degrees. The average diameter of lesions was 9 cm (range from 5 cm to 12.1 cm).Uterine cavity masses were found in 3 cases,all of which were solid masses and invaded into myometrium exhibiting disconnection or disappearance of the connection band of uterus,and one of which involved the bladder and right ureter,oviduct and ovary.The solid tumors in 3 cases showed isointensity on T1 WI and slight hyperin-tensity on T2 WI,1 of which was heterogenous with dilated vascular void signal in the inner and peripheral portion.In addition, myometrial mass was found in 1 case,which was cystic with septum and clear boundaries.The cystic tumor showed hypointensity on T1 WI and hyperintensity on T2 WI with hypointensive internal septum.There were 3 cases accompanied with uterine leiomyoma, and 1 case with pelvic lymph node metastasis.Conclusion Most of endometrial stromal sarcomas are located in uterine cavity,a few in myometrium.The tumors are solid,few can also show cystic,showing invasive growth into myometrium.The manifestation of low-grade endometrial stromal sarcoma has a certain characteristics on MRI,which is low or iso-signal intensity on T1 WI and high signal intensity on T2 WI,the signal intensity may be heterogeneous,so MRI can provide help for the correct diagnosis of the disease.