Choriocarcinoma is a highly malignant tumor of trophoblastic cells. About 50% of choriocarcinoma is secondary to uveitis, 25% is secondary to spontaneous abortion, more than 20% occurs in normal pregnancy, and less than 5% occurs in premature birth or ectopic pregnancy. This is because the trophoblast cells can remain hidden (in a non-proliferative state) for many years and only become active later for unknown reasons. The main clinical manifestations are persistent irregular vaginal bleeding after gravida, miscarriage or full-term delivery, and significantly elevated HCG concentrations in blood and urine. Prior to the 1960s, the disease had a high mortality rate, and in recent years improvements in chemotherapeutic regimens have led to a much improved prognosis for choriocarcinoma.