Biology:Intermediate trophoblast

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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.

Histomorphology

  • 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 show 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

Pathology

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

  • 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

  1. 1.0 1.1 1.2 1.3 1.4 1.5 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.