First Reported Histologically and Molecularly Confirmed Bilateral High-Grade Serous Ovarian Adenocarcinoma Metastasized to Placental Decidua of the Membranes.

A 43-year-old female presented with blood loss and persistent abdominal pain at 14 weeks of gestation. Ultrasound examination and subsequent magnetic resonance imaging (MRI) revealed bilateral multicystic uterine adnexa. Exploratory laparotomy was performed at 17 weeks of gestation and bilateral serous ovarian adenocarcinoma FIGO stage IIIC was diagnosed. Complete cytoreductive surgery (CRS) was not feasible at that moment. Nine days after the exploratory laparotomy, immature rupture of membranes and contractions occurred and she delivered a premature boy after 19 weeks of gestation. Pathological examination of the placenta revealed that her ovarian cancer metastasized to the membranes. We describe the first case of ovarian cancer metastasized to the decidua of the placental membranes with histological, immunohistochemical, and molecular confirmation. This case highlights the importance of conscientious evaluation of placenta and membranes in pregnant women with ovarian cancer.