Successful fertility preservation in stage II endometrial carcinoma with long-term progestin therapy: A case report

•Progestin therapy is a fertility-sparing treatment option for well-differentiated stage IA endometrioid carcinomas.•Progestin therapy is not recommended for stage II endometrioid carcinomas due to its high rate of failure.•We present a case of successful fertility preservation following long-term progestin therapy in stage II endometrioid carcinoma.•A decrease in Ki-67-positive tumor cells early after progestin exposure may predict the efficacy of progestin therapy. Progestin therapy is a fertility-sparing treatment option for well-differentiated stage IA endometrioid carcinomas without myometrial invasion. Here, we present a case of successful pregnancy and live birth following long-term progestin therapy in a patient with stage II well-differentiated endometrioid carcinoma. A 30-year-old nulliparous woman with an unremarkable medical history presented with abnormal uterine bleeding. A 45 mm mass was identified in the lower uterine segment. An endometrial biopsy revealed grade 1 endometrioid carcinoma, leading to a diagnosis of stage II uterine corpus cancer based on hysteroscopic findings. The patient refused surgical treatment and underwent oocyte retrieval and cryopreservation at another hospital. A subsequent endometrial biopsy revealed a marked reduction in the Ki-67 index from approximately 60 % to less than 10 %, suggesting the possibility of a hormone-sensitive tumor. The patient persistently refused surgery. Therefore, progestin therapy with medroxyprogesterone acetate (MPA) at a dose of 400 mg/day was initiated as a temporary measure until the patient would accept surgery. The tumor gradually reduced in size and eventually disappeared after 9 months. The MPA therapy was discontinued uneventfully after 20 months. Sixteen months after the discontinuation of MPA therapy, atypical endometrial hyperplasia was detected, and a second round of MPA therapy was initiated. Progestin retreatment was successful and was discontinued at 6 months. Four years after the initial treatment, the patient achieved pregnancy through timed intercourse and delivered a healthy baby at 38 weeks of gestation.