Gestational trophoblastic tumors are either invasive mole or malignant choriocarcinoma.

Choriocarcinoma is carcinoma of chorionic epithelium which goes into excessive invasive trophoblastic overgrowth and extensive penetration by trophoblastic elements, that can erode blood vessels and can penetrate into peritoneum also.

Choriocarcinoma leads to extensive necrosis and hemorrhage.
Invasive moles do not metastasize, whereas choriocarcinoma frequently metastasis to lungs, vagina, and brain.

Usually occur following hydatiform mole, abortion, and ectopic pregnancy.
 
Imaging

CT: Enlarged uterus with discrete, central and infiltrative mass with areas of necrosis and hemorrhage.

Ultrasound: Not specific and variable

Treatment depends on the type and stage of the tumor. Gestational choriocarcinoma has good prognosis with chemotherapy.