title: Expression of smooth-muscle actin in cultured cells from human plasmacytoid myoepithelioma.
abstract: OBJECTIVE
  The definition of plasmacytoid myoepithelioma, a neoplasm exhibiting myoepithelial differentiation, has been recently questioned. To better understand the histogenesis of this neoplasm, we searched for myoepithelial markers in histologic sections of plasmacytoid myoepithelioma and in a cell line (M1) derived from this same neoplasm.
  
  
  METHODS
  Expression of vimentin, pan-keratin (AE-3) and smooth-muscle actin was studied by immunohistochemistry in paraffin-embedded tissue and by immunofluorescence in M1 cells.
  
  
  RESULTS
  Plasmacytoid myoepithelioma tumor sections showed vimentin and AE-3 reactivity, but evidence of smooth-muscle actin was not seen. The cell line derived from this tumor also produced vimentin and cytokeratin. In addition, all cultured cells expressed smooth-muscle actin.
  
  
  CONCLUSIONS
  We demonstrated that cells derived from a case of plasmacytoid myoepithelioma appear to show full myoepithelial differentiation in vitro. Thus, they are myoepithelial-like cells in nature. The lack of myogenous differentiation in vivo could be due to an inhibitory process mediated by the extracellular matrix.
authors.affiliation: Department of Oral Pathology, School of Dentistry, University of São Paulo, Brazil.
authors.forename: R G
authors.initials: RG
authors.lastname: Jaeger
authors.forename: P T
authors.initials: PT
authors.lastname: de Oliveira
authors.forename: M M
authors.initials: MM
authors.lastname: Jaeger
authors.forename: V C
authors.initials: VC
authors.lastname: de Araújo
mesh_terms: D015100:3,3'-Diaminobenzidine; D000199:Actins / Q000032:analysis / Q000235:genetics*; D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor / Q000032:analysis; D002454:Cell Differentiation; D002863:Chromogenic Compounds; D004396:Coloring Agents; D005109:Extracellular Matrix / Q000502:physiology; D005260:Female; D019793:Fluorescein; D019085:Fluorescent Antibody Technique, Direct; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis / Q000235:genetics; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009208:Myoepithelioma / Q000473:pathology*; D010157:Palatal Neoplasms / Q000473:pathology*; D016612:Paraffin Embedding; D010950:Plasma Cells / Q000473:pathology; D014407:Tumor Cells, Cultured; D014746:Vimentin / Q000032:analysis / Q000235:genetics
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; D002863:Chromogenic Compounds; D004396:Coloring Agents; D014746:Vimentin; D015100:3,3'-Diaminobenzidine; D007633:Keratins; D019793:Fluorescein