Genesis of molar pregnancy: Neoplastic transformation of the inner cell mass with a case presentation

The hydatidiform mole is generally considered to be derived from placental elements due to a histological similarity between molar tissue and placental trophoblasts. A careful dissection was performed recently on a hysterectomy specimen containing an intact molar pregnancy. The presence of a membrane enclosing molar vesicles was demonstrated. To our knowledge, similar findings have not been described in the literature. A detailed morphological description of the contained molar pregnancy, along with an embryological review, will be presented. This case indicates that hydatidiform moles may originate from inside an embryonic sac, similar to an embryo, and not from the trophoblasts that surround the fetal sac. The ultrasound and the hysterogram study support the findings of the dissected specimen. Based on this case study, a model is constructed to illustrate a new concept regarding genesis of hydatidiform mole as a transformation of the embryonic inner cell mass.