Chronic tubal ectopic pregnancy with undetectable serum β-hCG mimicking a large ovarian endometrioma: A case report.

Ectopic pregnancy is usually associated with detectable serum β-human chorionic gonadotropin levels. A rare case of chronic tubal ectopic pregnancy with undetectable beta human chorionic gonadotrophin (β-HCG) that mimicked a large ovarian endometrioma is reported. A 34-year-old multiparous woman presented with prolonged abnormal uterine bleeding and chronic pelvic pain following a 45-day delay in menstruation. Imaging revealed a large complex left adnexal mass measuring 12 × 10 × 7 cm, highly suggestive of ovarian endometrioma. Surgical exploration demonstrated a densely adherent adnexal mass requiring left salpingo-oophorectomy. Histopathological examination confirmed chronic tubal ectopic pregnancy. This case highlights that ectopic pregnancy should remain in the differential diagnosis of adnexal masses even when serum β-hCG is undetectable.