Intermediate trophoblast is a distinct subtype of

trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the pl ...

ic tissue that arises from the

cytotrophoblast "Cytotrophoblast" is the name given to both the inner layer of the trophoblast (also called layer of Langhans) or the cells that live there. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo ...

. 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 The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...

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 Exaggeration is the representation of something as more extreme or dramatic than it really is. Exaggeration may occur intentionally or unintentionally. Exaggeration can be a rhetorical device or figure of speech. It may be used to evoke str ...

(EPS): implantation site IT *

Placental site nodule A placental site nodule (PSN) is benign remnant from a previous pregnancy. Presentation They are typically asymptomatic and found incidentally. Pathology PSNs are intermediate trophoblastic remnants. Diagnosis PSNs are diagnosed by examining t ...

(PSN): chorionic-type IT *

Placental site trophoblastic tumour Placental site trophoblastic tumor is a form of gestational trophoblastic disease, which is thought to arise from intermediate trophoblast. The tumor may secrete human placental lactogen, and result in a false-positive pregnancy test. A placental ...

(PSTT): implantation site IT *

Epithelioid trophoblastic tumour Epithelioid trophoblastic tumor (ETT) is a gestational trophoblastic disease with about 110 case reports in the literature. It is a trophoblastic tumor of neoplastic chorionic type associated with the intermediate trophoblast. Signs and symptoms ...

(ETT): chorionic-type IT

References

{{Extraembryonic and fetal membranes Embryology