Subchorionic thrombohematoma (Breus’ Mole)
A subchorionic thrombohematoma is a large maternal clot that separates the chorionic plate from the villous chorion. It was first described by Breus in 1892 in first trimester miscarriages. The fetal survival rate with a massive subchorionic thrombohematoma is between 30% and 50%.
A subchorionic thrombohematoma is generally a chronic and gradually progressive process that invariably results in intra-uterine growth restriction. Nyberg et al have referred to this placental hemorrhage as a ‘pre-placental hematoma’. Since trophoblastic villi are not detached from the uterine wall, a preplacental hematoma is not a placental abruption.
The differential diagnosis of a subchorionic thrombohematoma would include placentamegaly from either non-immune hydrops or a placental abruptio with diffusion of maternal blood throughout the placenta. The utilization of color Doppler would confirm the presence of placental flow in cases of placentamegaly secondary to non-immune hydrops. However, depending upon the extent of intraplaental hemorrhage, color Doppler may or may not visualize vessels within an intraplacental abruption. Color Doppler will not detect any vessels within a subchorionic thrombohematoma.
The placenta is thickened and has an irregular cystic/solid appearance.