Abstract
Low-grade endometrial stromal sarcoma (LG-ESS) is a rare uterine tumor that sometimes recurs and advances. Hormonal treatment, especially high-dose progestins and aromatase inhibitors (AIs), has demonstrated efficacy against these tumors. Because the standard treatment period is uncertain and hormonal treatment is effective, hormonal agents are likely to be used long-term, especially when a residual tumor is present. However, the long-term use of high-dose progestins and AIs may cause thromboembolism, as well as musculoskeletal stiffness and pain. Dienogest, a relatively new progestin, has demonstrated safety after long-term administration; it also appears to have a more favorable long-term safety profile compared with other progestins and AIs. We encountered a young patient with recurrent LG-ESS that metastasized to the liver and exhibited resistance to high-dose medroxyprogesterone acetate (MPA). The patient was successfully treated with dienogest monotherapy. This is the first report describing the efficacy of dienogest against recurrent and metastatic LG-ESS that is resistant to MPA and other agents.