Extrauterine Epithelioid Trophoblastic Tumor (ETT) Arising from an Antecedent Undiagnosed Molar Pregnancy Presenting as an Adnexal mass: A Case Report

Introduction/Objective Epithelioid trophoblastic tumor (ETT) is an extremely rare neoplasm derived from chorionic type intermediate trophoblast. ETT usually follows an antecedent term pregnancy but can also follow spontaneous abortions or molar pregnancy. ETT most often arises from the endometrium, followed by the cervix. Extrauterine ETT are extremely rare, with few cases reported in literature. Methods/Case Report A 41-year-old woman with three term pregnancies presented with abdominal pain, ten years after her last pregnancy. Imaging findings of a 3.5 cm adnexal mass coupled with an elevated serum β-hCG (~ 900 mIU/ml), led to the suspicion of an ectopic pregnancy. Hysterectomy with salpingectomy revealed a 4.7 cm, tan- yellow, necrotic mass in the adnexal region abutting but distinct from the uterine serosa. Histologic evaluation showed a well- circumscribed tumor with pushing borders. The tumor cells were epithelioid with well-defined eosinophilic cytoplasm, monomorphic nuclei, frequent mitosis, and abundant geographic necrosis. The tumor cells were positive for β-hCG, GATA-3, PLAP and inhibin, with focal weak staining squamous markers p63 and p40. DNA fingerprinting analysis, performed to confirm the diagnosis of ETT, revealed a homozygous tumor with two copies of non-maternal genes indicating that the antecedent index gestation giving rise to the tumor was an undiagnosed hydatidiform mole. Following surgery, serum β-hCG levels were normal and the patient is currently on surveillance. Results (if a Case Study enter NA) NA Conclusion We present an extremely rare case of extrauterine ETT arising from a previously undetected molar pregnancy. The diagnosis should be suspected when a mass is observed at extrauterine sites with elevated β-hCG levels in patients with or without vaginal bleeding. Histologic differential of squamous cell carcinoma needs to be ruled out with immunostains. Due to its rarity and highly variable presentation, this entity remains a diagnostic challenge. DNA fingerprinting analysis demonstrating non-maternal genes can help confirm the diagnosis of ETT.