Multimodal treatment, including assisted reproductive technology, is necessary in young patients with advanced borderline ovarian tumors. However, the details of long-term follow-up cases have not been reported. In this report, a 19-year-old patient presented with a stage IIIC serous borderline tumor. The patient underwent five fertility-sparing surgeries. The tumor did not respond to any of the three lines of chemotherapy administered. Serological and radiological responses were observed following hormonal treatment with leuprorelin, followed by a fourth surgery. Before the planned fifth surgery for complete resection of both adnexa, cryopreservation of the fertilized eggs was performed. At age 36, when the disease-free interval exceeded the previous one, we proposed embryo transfer; however, she declined fertility treatment. The patient had developed rheumatoid arthritis and childbirth not a priority. The patient had lived without any evidence of disease for 7 years following the last surgery and 20 years after the initial visit.© 2023 Japan Society of Obstetrics and Gynecology.
