Endometrial stromal sarcoma is known to be a hormone-dependent tumor. Efficacy of hormonal therapy including high-dose progestins, aromatase inhibitors or gonadotropin-releasing hormone analogs has been reported. We report a case of recurrent endometrial stromal sarcoma, the tumor cells of which were strongly positive for CD10, estrogen and progesterone receptors. Although almost all of the pelvic tumors infiltrating the rectum or pelvic side wall remained, the patient is alive with slight disease 9 years and 6 months after the initial failure. During the treatment period of 4 years and 3 months, the patient was treated exclusively with dydrogesterone at a daily dose of 10 mg and the tumor clinically disappeared. Dydrogesterone at a daily dose of 10 mg may be effective in treating low-grade endometrial stromal sarcoma.
