Gestational trophoblastic tumors may be classified as follows:[1]

• Hydatidiform mole.
• Invasive mole (chorioadenoma destruens).
• Choriocarcinoma.
• Placental-site trophoblastic tumor.

Hydatidiform mole

Hydatidiform mole is defined as products of conception that lack an intact fetus and show gross cyst-like swellings of the chorionic villi caused by an accumulation of fluid. There is disintegration and loss of blood vessels in the villous core.

Invasive mole

Invasive mole (chorioadenoma destruens) is a locally invasive, rarely metastatic lesion characterized microscopically by trophoblastic invasion of the myometrium with identifiable villous structures. Microscopically, this lesion is characterized by hyperplasia of cytotrophoblastic and syncytial elements and persistence of villous structures.

Choriocarcinoma

Choriocarcinoma is a malignant tumor of the trophoblastic epithelium. Uterine muscle and blood vessels are invaded with areas of hemorrhage and necrosis. Columns and sheets of trophoblastic tissue invade normal tissues and spread to distant sites, the most common of which are lungs, brain, liver, pelvis, vagina, spleen, intestines, and kidney.

Placental-site trophoblastic tumor

Placental-site trophoblastic disease is an extremely rare tumor arising from the placental implantation site and resembles an exaggerated form of syncytial endometritis. Trophoblastic cells infiltrate the myometrium, and there is vascular invasion. Human placental lactogen is present in the tumor cells, while immunoperoxidase staining for human chorionic gonadotropin (hCG) is positive in only scattered cells, and serum hCG is relatively low.[1]

References

1. Lurain JR: Gestational trophoblastic tumors. Semin Surg Oncol 6 (6): 347-53, 1990.  [PUBMED Abstract]