title: Huge clusters of embryonic stem cells in human embryos: a morphologic study.
abstract: BACKGROUND
  Nothing is known about huge clusters (HC) of embryonic stem cells (ESC) in human fetal organs (HFO).
  
  
  OBJECTIVE
  To know the status of HC-ESC in HFO.
  
  
  METHODS
  Morphology and immunohistochemistry (IHC) in 32 HFO of 7-40 gestational weeks (GW).
  
  
  RESULTS
  HC-ESC were seen in many HFO including central nervous system, spinal cords, spine, soft tissue, bone, skin, thyroid, lung, liver, pancreas, gall bladder, extrahepatic bile duct, adrenal, kidney, bladder, foregut, midgut, hindgut, female and male genital organs, and neurons. HC-ESC's were composed of two populations depending on constituting cells. One were large cells with ample acidophilic cytoplasms with vesicular nuclei and nucleoli. The other were small cells with scant cytoplasm with hyperchromatic nuclei without nucleoli, resembling lymphocytes. The HC-ESC were frequently showed neuronal differentiation. HC-ESC were positive for NCAM, synaptophysin, NSE, chromogranin, PDGFRA, AFP, ErbB2, bcl-2, KIT, MET. They were negative for CD45, CD3, CD20, EMA, CEA, CA19-9, cytokeratin (CK) 7, CK8, CK18, CK19, MUC1, MUC2, MUC5AC, and MUC6. The mean Ki-67 labeling index (LI) was 13% ± 7%. HC-ESC showed a little glycogen but lacked mucins. These HC-ESC were seen in 7-25 GW, and they were rarely seen in 26-40 GW.
  
  
  CONCLUSIONS
  The morphology, IHC, and ontogeny of HC-ESC were described.
authors.affiliation: Department of Pathology, Shizuoka City Shimizu Hospital, Shizuoka, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Terada
mesh_terms: D004622:Embryo, Mammalian / Q000166:cytology* / Q000648:ultrastructure; D053595:Embryonic Stem Cells / Q000648:ultrastructure*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D038081:Organogenesis
keywords: development; differentiation; embryo; embryonic stem cells; fetus; human