The term malignant staphyloma, which is less commonly used nowadays, is also known as erosive staphyloma because of the erosive nature of the staphyloma. It is a malignant act because the trophoblastic cells of the gravida erode the tissue below the endometrium and also enter the uterine vessels and spread throughout the body along the vessels. It used to be called malignant staphyloma, but it is not cancer. In addition, there is a trophoblastic disease of pregnancy called choriocarcinoma, which is very similar to cancer, but is not really cancer either. Most malignant choriocarcinomas can be cured with aggressive treatment and patients can have children again, so it is not a disease that can be equated with cancer.