Supplementary Material for: Characteristics of epithelioid trophoblastic tumor: endoscopic and magnetic resonance imaging findings

Introduction: Epithelioid endothelial tumor (ETT) is an extremely rare tumor that mostly occurs in women of reproductive age. The diagnosis tends to be delayed because it often necessitates a total hysterectomy. Therefore, it is important to understand ETT's macroscopic and imaging findings. Here, we report a case of ETT with detailed macroscopic and imaging findings. Case presentation: A 39-year-old woman with positive pregnancy test results was admitted to a nearby hospital. No gestational sac was found in the uterus, and magnetic resonance imaging (MRI) revealed a cystic mass of approximately 7 cm that extended continuously from the anterior wall of the lower uterine segment into the pelvic cavity. She underwent laparoscopic and hysteroscopic surgeries for a ruptured cervical pregnancy. Pathology of the specimens obtained from this surgery did not allow for the diagnosis of ETT. Two months after the surgery, as the serum human chorionic gonadotropin β subunit (β-HCG) level did not decrease, she was diagnosed with low-grade gestational trophoblastic neoplasia (GTN), leading to the administration of chemotherapy. After three regimens of chemotherapy over 9 months, β-HCG level decreased but did not reach normal levels. Ultimately, a total hysterectomy was performed. The pathological diagnosis was ETT with choriocarcinoma. A literature review revealed several cases similar to ours. Conclusion: ETT in the lower uterus often perforates the myometrium and forms cystic lesions in the retroperitoneal space or subserosa. The MRI and laparoscopic/hysteroscopic findings in this case may contribute to the early diagnosis of ETT.