Intermediate trophoblast

Micrograph showing intermediate trophoblasts. H&E stain.

Implantation site intermediate trophoblast. Low molecular weight cytokeratin stain.

Intermediate trophoblast is a distinct subtype of trophoblastic tissue that arises from the cytotrophoblast.^[1]

It is sub-categorized by location:^[1]

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.

Villous intermediate trophoblast^[1]
- polyhedral and uniform nuclei
- prominent cell border; abundant eosinophilic to clear cytoplasm
- cohesive growth
Implantation site intermediate trophoblast^[1]
- 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^[1]
- round to polyhedral nuclei, may multinucleation
- abundant eosinophilic to clear cytoplasm
- cohesive growth

Intermediate trophoblasts are thought to be the cell of origin for:^[1]

1 2 3 4 5 6 Shih IM, Kurman RJ (January 2001). "The pathology of intermediate trophoblastic tumors and tumor-like lesions". Int. J. Gynecol. Pathol. 20 (1): 31–47. doi:10.1097/00004347-200101000-00004. PMID 11192071.

Membranes of the fetus and embryo

Embryo	Trophoblast Cytotrophoblast Syncytiotrophoblast Intermediate trophoblast Allantois Decidua Decidual cells Chorionic villi/Intervillous space Amnion sac cavity

Fetus	Umbilical cord Umbilical artery Umbilical vein Wharton's jelly

Circulatory	Placenta Chorion

Other	Blastocoel Heuser's membrane Vitelline duct Gestational sac

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