What Causes It A complete hydatidiform or invasive mole occurs when a single sperm fertilizes an egg without a nucleus. The chromosomes in the sperm duplicate, resulting in an abnormal embryo that has only male genetic material. A mole can also occur when two sperm fertilize a single egg. A mole develops from the abnormally fertilized egg and is characterized by a lack of a normal fetus and by many small fluid-filled cysts.
The cause of choriocarcinoma is uncertain. It can arise from a normal pregnancy, a miscarriage, a tubal pregnancy or from either type of mole.
How It Spreads Hydatidiform moles generally stay confined to the endometrial cavity. When it begins to invade the wall of the uterus , it is called an invasive mole. Occasionally a hydatidiform mole and an invasive mole can spread to distant sites, most typically to the lung.
An invasive mole can penetrate the full thickness of the uterine wall and rupture, resulting in severe intra-abdominal or vaginal bleeding. Invasive moles can also metastasize, most commonly to the vagina and lung. This may be confusing since women with proven invasive moles who have metastases may also have choriocarcinoma. Although an invasive mole is locally more aggressive than a non-invasive mole, it is no more likely to be complicated by choriocarcinoma.
Choriocarcinoma can spread virtually anywhere in the body but most commonly spreads to the lung, the lower genital tract (cervix, vagina and vulva), the brain, liver, kidney and the gastrointestinal tract.
