A form of gestational trophoblastic neoplasia similar to a hydatidiform mole but with deep invasion into the myometriumand histologically characterized hyperplasia of trophoblasts, generalized cystic degeneration of chorionic villi and the presence of molar villi in the myometrium and/ or uterine blood vessels. Indicative signs include persistent unexplained metrorrhagia or secondary increase, stagnation, or non-normalization at 6 months of total serum chorionic gonadotropin (hCG) levels after evacuation of a hydatidiform mole. Metastases (in the lungs or vagina) may be observed. [from
ORDO]