Gestational trophoblastic diseases (GTD) represent a spectrum of tumors and tumor-like conditions involving abnormal proliferation of placental tissue. GTD includes hydatidiform mole (complete and partial), invasive mole, choriocarcinoma, and placental site trophoblastic tumor. Complete moles occur when an egg is fertilized by two sperm or a sperm that failed meiosis, resulting in no fetal development. Partial moles have some fetal development but also placental abnormalities. Diagnosis involves ultrasound, beta-HCG levels, and biopsy. Treatment depends on the type but generally involves surgical evacuation and chemotherapy to remove trophoblastic tissue and prevent metastasis.