Abstract: Gestational trophoblastic tumors are a heterogeneous and aggressive group of neoplasms. Choriocarcinoma, an extremely rare subset of gestational trophoblastic tumor, is often metastatic at diagnosis and typically follows a pregnancy that is either ectopic or molar. We present a critical review of choriocarcinomas with an emphasis on choriocarcinomas of ovarian origin which are even more uncommon with an incidence estimated at 1 per 369 million. This manuscript also includes a case of a woman with polycystic ovarian syndrome who required assisted conception to conceive her daughter and then developed a rare extrauterine gestational ovarian choriocarcinoma eighteen months following her antecedent healthy pregnancy with uncomplicated delivery. Many aspects of this presentation are unique, even for such an extraordinary tumor; some of these include the absence of vaginal bleeding, the presence of unilateral pulmonary metastases, and an overwhelmingly positive serum β-hCG with a negative urine β-hCG. While such a discrepancy in urine and serum β-hCG has been reported in gestational trophoblastic disease following molar pregnancies, to our knowledge it has not yet been reported in choriocarcinomas following a normal pregnancy.Abstract: Gestational trophoblastic tumors are a heterogeneous and aggressive group of neoplasms. Choriocarcinoma, an extremely rare subset of gestational trophoblastic tumor, is often metastatic at diagnosis and typically follows a pregnancy that is either ectopic or molar. We present a critical review of choriocarcinomas with an emphasis on choriocarcinoma...Show More