Invasive Partial Hydatidiform Mole Presenting As Cesarean Scar Pregnancy: A Case Report

Invasive hydatidiform mole is a rare subtype of gestational trophoblastic disease characterized by myometrial invasion and the potential for significant morbidity. Cesarean scar pregnancy (CSP) is an uncommon type of ectopic pregnancy with increasing incidence due to the rise in cesarean delivery rates. The coexistence of an invasive hydatidiform mole implanted in a cesarean scar is exceptionally rare and poses significant diagnostic and therapeutic challenges. This is a case of a 32-year-old Malay woman with a prior history of cesarean section who presented with per-vaginal bleeding in early pregnancy. Assessment revealed a viable gestational sac with vesicles within, suggesting that a partial hydatidiform mole had implanted at the cesarean scar site. Serum beta-human chorionic gonadotropin (β-hCG) levels were markedly elevated (>200,000 IU/L). MRI of the pelvis was reported as suggestive of partial invasive molar pregnancy with serosal breach through the cesarean scar and bladder invasion, along with a fetus seen, and proceeded with six cycles of methotrexate and folinic acid regimen. Serum β-hCG levels reduced accordingly (368 IU/L pre-sixth cycle and prior surgery). Proceeded with total abdominal hysterectomy, bilateral salpingectomy, and histopathological examination confirmed the diagnosis of an invasive hydatidiform mole arising from a CSP. The patient was managed with a multidisciplinary approach with close β-hCG surveillance. Clinical and biochemical remission was achieved. Invasive hydatidiform mole presenting as a CSP is extremely rare. Early recognition through imaging, β-hCG monitoring, and histopathology is crucial to prevent life-threatening complications. Prompt multidisciplinary management and careful follow-up are essential for favorable outcomes.