Ovarian serous borderline tumors with recurrent or extraovarian lesions: a Japanese, retrospective, multi-institutional, population-based study

Background Ovarian serous borderline tumors (SBT) are typically unilateral and are primarily treated using hysterectomy and bilateral salpingooophorectomy (SO). However, most young patients prefer fertility-sparing surgeries (FSS) with tumorectomy or unilateral SO. Micropapillary morphology and invasive implants have been designated as histopathological risk indicators for recurrence or metastasis, but their clinical impact remains controversial because of limitations like diagnostic inconsistency and incomplete surgical staging. Methods A nationwide multi-institutional population-based retrospective surveillance was conducted with a thorough central pathology review to reveal the clinical features of SBT. Of 313 SBT patients enrolled in the Japanese Society of Clinical Oncology's Surveillance of Gynecologic Rare Tumors, 289 patient records were reviewed for clinical outcomes. The glass slides of patients at stage II–IV or with recurrence or death were re-evaluated by three gynecological pathologists. Result The 10-year overall and progression-free survival (PFS) rates were 98.6% and 92.3%. The median recurrence period was 40 months and 77.0% was observed in the contralateral ovary within 60 months. Patients aged ≤ 35 years underwent FSS more frequently and relapsed more (p < .001). A clinic-pathological analysis revealed diagnosis during pregnancy, FSS, and treatment at non-university institutes as well as advanced stage and large diameter were independent risk factors of recurrence. Among patients having pathologically confirmed SBTs, PFS was not influenced by the presence of micropapillary pattern or invasive implants. Conclusion The recurrence rate was lower in this cohort than previous reports, but the clinical impacts of incomplete resection and misclassification of the tumor were still significant on the treatment of SBT.