Trophoblast
Chorionic villi are part of a normal pregnancy. They are derived from the conceptus, i.e. NOT maternal.
Tumours arising from the trophoblast are dealt with in gestational trophoblastic disease.
Chorionic villi 101
- Maternal blood is around villi.
- Fetal blood (nucleated (fetal) RBCs) in the villi.
Basic histology
- Outer layer of villus: syncytiotrophoblasts.
- Beneath syncytiotrophoblast (and closer to fetus) cytotrophoblasts.
Chorionic villi 102
- Syncytiotrophoblasts (eosinophilic cytoplasm with vacuoles (contain hCG), multiple hyperchromatic nuclei).
- Large + many irreg. or lobular hyperchromatic nuclei.
- Eosinophilic vacuolated cytoplasm (contains hCG).
- Closest to mom - covers cytotrophoblast.[1]
- Cytotrophoblasts (polygonal shape, distinct borders, clear cytoplasm, in cords, single nucleus).
- Polygonal shaped cells in cords/masses.
- Distinct cell borders.
- Covered by syncytiobrophoblast[2] - closer to fetus than syncytiotrophoblasts.
- Clear cytoplasm.
- Single uniform nucleus.
Intermediate trophoblast
General
- Abbreviated: IT.
- Thought to be the cell of origin for:[3]
- Exaggerated placental site (EPS).
- Placental site nodule (PSN).
- Placental site trophoblastic tumor (PSTT).
- Epithelioid trophoblastic tumor (ETT).
Subtypes
Three subtypes of IT are recognized:[3]
- Implanation site IT.
- Villous IT.
- Chorionic-type IT.
Microscopic
Features:
- Large cells.
- Eosinophilic cytoplasm.
- May be multi-nucleated.
IHC
Features:[4]
- hPL (human placental lactogen) +ve.
- beta-hCG -ve.
- Keratin +ve.
- EMA +ve in 2nd & 3rd trimester.
Notes:
- Cytotrophoblast and syncytiotrophoblast - keratin +ve.[4]
Age of villi
Young villi
- Do not have blood vessels.
- No syncytial knots.
Old villi
- Blood vessels present and at the periphery of villus - contain nucleated (fetal) RBCs.
- Syncytial knots.
Trophoblast table
Based on Shih et al.:[3]
Cytotrophoblast | Syncytiotrophoblast | Villous intermediate trophoblast |
Implanation site intermediate trophoblast |
Chorionic-type intermediate trophoblast | |
Nuclear features | round, small | multinucleated | polyhedral | pleomorphic +/-multinucleation (occasional), +/-nucleoli |
round / polyhedral |
Cell borders | well-defined | poorly defined (?) | well-defined | moderately-defined | poorly defined (?) |
Cytoplasm | minimal, clear to granular | abundant, vacuolated | abundant & eosinophilic to clear | abundant & eosinophilic | abundant & eosinophilic |
Location | villi - deep to syncytiotrophoblast |
villi - superficial to cytotrophoblast - nearest to maternal blood |
villi | implanatation site | chorion |
Function | stem cell | produces hormones | ??? | anchor placenta | ??? |
IHC | beta-hCG ??? | beta-hCG | ??? | LMWK, inhibin | ??? |
Image | [1] |
See also
References
- ↑ http://upload.wikimedia.org/wikipedia/commons/4/45/Gray37.png
- ↑ http://upload.wikimedia.org/wikipedia/commons/4/45/Gray37.png
- ↑ 3.0 3.1 3.2 Shih IM, Kurman RJ (January 2001). "The pathology of intermediate trophoblastic tumors and tumor-like lesions". Int. J. Gynecol. Pathol. 20 (1): 31–47. PMID 11192071.
- ↑ 4.0 4.1 Yeh IT, O'Connor DM, Kurman RJ (May 1990). "Intermediate trophoblast: further immunocytochemical characterization". Mod. Pathol. 3 (3): 282–7. PMID 1694585.