Asian Research Journal of Gynaecology and Obstetrics

Background: Caesarean scar ectopic pregnancy (CSEP) is a rare, life-threatening form of ectopic gestation in which implantation occurs within the myometrium of a previous hysterotomy scar. Because of its atypical hypervascular projections, it may mimic other serious uterine pathologies, leading to major diagnostic and therapeutic errors.

Case Presentation: This report describes a 34-year-old multiparous woman (para 2, live 2, with two previous caesarean deliveries) who presented with prolonged abnormal uterine bleeding, severe anaemia, and a paradoxically negative qualitative urine pregnancy test despite an extraordinarily high quantitative serum β-hCG level of 93,484 mIU/mL. Initial advanced imaging, including ultrasonography and magnetic resonance imaging (MRI), suggested a high-grade uterine leiomyosarcoma, gestational trophoblastic neoplasia (GTN), or an acquired uterine arteriovenous malformation (AVM).

Despite a rapid, spontaneous 50% decline in serum β-hCG over 48 hours, persistent, intractable vaginal bleeding led to a decision to perform suction evacuation. This was followed by immediate, life-threatening uterine haemorrhage that did not respond to conservative measures and necessitated an emergency laparotomy. Intraoperatively, a Type I (endophytic) CSEP was identified within the lower uterine segment scar and was successfully excised with preservation of the uterus.

Conclusion: This case highlights the deceptive biochemical mimicry and radiological overlap associated with CSEP. It emphasises the need for caution when evaluating hypervascular pelvic masses and the importance of quantitative serum assays when a qualitative urine test may be affected by the hook effect.