Atypical epithelioid trophoblastic lesion with cyst and fistula formation after a cesarean section: a rare form of gestational trophoblastic disease.

We report 2 unusual cases of gestational trophoblastic disease from chorionic-type intermediate trophoblastic cells after a Cesarean section. A 32-year-old woman presented with a 2-year history of vaginal bleeding, while a 41-year-old woman presented with a pelvic mass. Both patients had cystic lesions with a fistula formation beneath their Cesarean scars in the anterior uterine isthmus. Microscopically, both lesions were lined with multiple layers of intermediate trophoblastic cells without penetration into the surrounding myometrium, endometrium, or blood vessels. The trophoblastic cells were generally bland. However, a subset of trophoblastic cells showed large, hyperchromatic nuclei in some areas. The trophoblastic cells were p63 positive and human placental lactogen negative. The Ki67 indexes were 12.7% and 8.6%, respectively. We propose their description as atypical epithelioid trophoblastic lesions with cyst and fistula formation after a Cesarean section.