Placental Histomorphology in a Case of Double Trisomy 48,XXX,+18.

In addition to convoluted outlines of chorionic villi, villous trophoblastic pseudoinclusions, and clusters of villous cytotrophoblasts, the previously unreported focal pseudovillous papilliform trophoblastic proliferation of the undersurface of the chorionic plate and clustering of perpendicularly oriented sclerotic chorionic villi in the chorion laeve were observed in this double trisomy case. More cases have to be examined to show if the histology is specific for this double trisomy.