Choriocarcinoma is a form of cancer of the uterine placenta in females and, much more rarely, in the testicles of males and ovaries of females. Although it is very malignant and aggressive, the placental form responds well to chemotherapy even after metastasis. The rarer forms generally do not respond well to treatment.
Choriocarcinoma is almost always set off by a pregnancy and occurs in somewhere between one in 15,000 and one in 30,000 pregnancies. In up to 30% of cases, it is a complication of a normal pregnancy. However, half of cases occur when an unfertilized egg implants in the endometrial cells of the uterus, resulting in no actual possibility of birth, but the development of a placenta in order to support a non-existent fetus. In other cases, it is set off by an ectopic pregnancy or miscarriage.
From its initial site, it almost always spreads to the lungs, where it can be seen on x-rays. If it does not spread to the lungs, chemotherapy is almost always effective and, even after it spreads, chemotherapy can be effective in 95% of cases. In some cases, a hysterectomy is performed to remove the uterus, but this is only common with older women or women who are sure they want no further children.