Choriocarcinoma, also called chorionic carcinoma or chorioblastoma, is a malignant and aggressive tumour caused by uncontrolled growth of troboblast cells. These cells are responsible for the formation of the placenta and the attachment of the embryo to the uterus.
Normally, choriocarcinoma formation occurs in the woman's uterus after fertilisation. However, this type of cancer has sometimes been detected in the testicles and ovaries.