Intestinal-Type Mucinous Borderline Ovarian Tumour in Pregnancy With a Non-invasive Omental Mucinous Deposit: A Case...

Borderline ovarian tumours during pregnancy are uncommon and require a balance between maternal oncological safety, fetal well-being, and fertility preservation. Intestinal-type mucinous borderline ovarian tumours associated with a non-invasive omental mucinous deposit are particularly unusual. A 31-year-old primigravida was found to have an asymptomatic 9.8 cm adnexal mass at 11 weeks' gestation. Serial ultrasonography showed no papillary projections, solid components, ascites or abnormal Doppler flow; however, the mass progressively enlarged to 15 cm by 36 weeks. At 37 weeks, induction of labour for uncontrolled hypertension was complicated by fetal distress, necessitating emergency caesarean delivery. Intraoperative examination revealed a 15 cm thin-walled, biloculated left ovarian cyst without grossly suspicious features. Fertility-sparing cystectomy and ovarian reconstruction were performed, during which inadvertent cyst rupture occurred. The macroscopically normal omentum was biopsied. Histopathological examination confirmed an intestinal-type mucinous borderline ovarian tumour. Immunohistochemistry showed diffuse cytokeratin 7 (CK7) positivity, focal CK20 and Caudal-type homeobox transcription factor (CDX2)positivity, and negative oestrogen receptor​​​​​​​ (ER)and paired-box family of transcription factor​​​​​​​ (PAX8) staining, supporting a primary ovarian tumour with intestinal-type differentiation. The omental specimen contained a non-invasive mucinous epithelial deposit without evidence of malignancy, considered most likely related to surgical spillage. Following counselling regarding the risks of recurrence and progression, the patient elected conservative surveillance and remained clinically and radiologically free of recurrence during short-term postpartum follow-up and is planned for long-term surveillance 3 monthly follow up for 2 years, then 6-monthly up to at least 5 years. If fertility is no longer desired, completion surgery will be discussed. This case demonstrates that reassuring sonographic and intraoperative morphology does not exclude a borderline ovarian tumour when an adnexal mass progressively enlarges. Fertility-sparing management may be appropriate in carefully selected patients, provided that recurrence risk and the need for long-term surveillance are clearly addressed.