Intermediate trophoblast is a distinct subtype of trophoblastic tissue that arises from the cytotrophoblast. It is sub-categorized by location: Villous intermediate trophoblast: at anchoring villi of trophoblastic column Implantation site intermediate trophoblast: at implantation site (or basal plate), differentiated from villous intermediate trophoblast Chorionic-type intermediate trophoblast at chorionic laeve of fetal membrane, differentiated from villous intermediate trophoblast Function The function of the implantation site intermediate trophoblast is to anchor the placenta to the maternal tissue. Histomorphology Villous intermediate trophoblast polyhedral and uniform nuclei prominent cell border; abundant eosinophilic to clear cytoplasm cohesive growth Implantation site intermediate trophoblast pleomorphic irregular nuclei, large and hyperchromatic, may multinucleation abundant eosinophilic to amphophilic cytoplasm infiltrative growth (splitting muscle, replacing vascular wall ...etc) Chorionic-type intermediate trophoblast round to polyhedral nuclei, may multinucleation abundant eosinophilic to clear cytoplasm cohesive growth Pathology Intermediate trophoblasts are thought to be the cell of origin for: Exaggerated placental site (EPS): implantation site IT Placental site nodule (PSN): chorionic-type IT Placental site trophoblastic tumour (PSTT): implantation site IT Epithelioid trophoblastic tumour (ETT): chorionic-type IT References Embryology