Spontaneous rupture of a mucinous borderline ovarian tumour in late pregnancy: a case report

Background Mucinous borderline ovarian tumours (mBOTs) during pregnancy are rare, and spontaneous rupture in the third trimester is a life-threatening emergency. Most adnexal masses with stable imaging are managed conservatively, which risks delayed intervention. The optimal surveillance and surgical strategies for mBOTs in late pregnancy remain unclear. Case description A 26-year-old primigravida with a 10-year history of an adnexal cyst presented at 29 + 1 weeks with acute abdominal pain. Serial ultrasounds documented tumour growth from 4.0 cm pre-pregnancy to 17.46 cm ( Figure 1 ), with morphological deterioration. Emergency laboratory tests revealed elevated AFP, CA19-9, and HE4 levels, which, combined with imaging findings, raised suspicion of a neoplastic process. Emergency laparotomy at 29 + 1 weeks revealed a ruptured right ovarian tumour with 1000 mL of mucinous ascites. Frozen section suggested a borderline tumour. Fertility-sparing staging surgery (adnexectomy, peritoneal biopsies, omentectomy) was performed. Postoperative pathology, confirmed by expert consultation, diagnosed a mBOT (atypical proliferative mucinous tumour) with 85% borderline components, Ki-67 ~30%, and no intraepithelial carcinoma, no microinvasion, and no invasive carcinoma The patient recovered uneventfully and she had a spontaneous vaginal delivery at 39 + 2 weeks of gestation, delivering a healthy full-term male infant (2, 840 g, Apgar 10/10). Postpartum imaging and tumour markers showed no evidence of residual disease. Conclusion This case suggests that conventional expectant management may be inadequate for pre-pregnancy cystic adnexal masses with growth trajectory, highlights the importance of multidisciplinary evaluation and stratified monitoring, and illustrates that emergency fertility-sparing staging surgery in the third trimester is feasible and achieved favourable maternal and neonatal outcomes in a patient with a ruptured mucinous borderline tumour, while preserving fertility.