title: MOC-31/Ep-CAM immunoreactivity in Merkel cells and Merkel cell carcinomas.
abstract: OBJECTIVE
  To evaluate the monoclonal antibody MOC-31 in Merkel cell carcinomas and normal Merkel cells. Merkel cell carcinoma is a rare and aggressive tumour that occurs mainly in elderly individuals. The histological diagnosis of Merkel cell carcinoma can be difficult because it looks similar to other small blue cell tumours, particularly skin metastases of small-cell lung carcinomas. This antibody recognizes the epithelial cell adhesion molecule (Ep-CAM), that has been assigned to the small cell lung cancer cluster 2 of antibodies. To the best of our knowledge, immunostaining for MOC-31/Ep-CAM has not been previously described in Merkel cells or Merkel cell carcinomas.
  
  
  RESULTS
  Thirty-one cases of Merkel cell carcinoma and three samples of normal human fingertip were selected to analyse the expression of MOC-31/Ep-CAM by immunohistochemistry. A high number of Merkel cell carcinomas (21/31, 67.7%) showed intense and readily interpretable positivity. Immunostaining was diffuse or focal and always localized to the plasma membrane. Normal Merkel cells of human fingertip also showed plasma membrane immunoreactivity for MOC-31/Ep-CAM.
  
  
  CONCLUSIONS
  The demonstration of positivity for MOC-31/Ep-CAM in Merkel cell carcinomas precludes the use of this immunohistochemical marker to distinguish between tumours and skin metastases of small-cell lung carcinoma.
authors.affiliation: Department of Morphological Sciences, Faculty of Medicine, University Clinical Hospital of Santiago de Compostela, Spain. cm-tgc@usc.es
authors.forename: T
authors.initials: T
authors.lastname: García-Caballero
authors.forename: E
authors.initials: E
authors.lastname: Pintos
authors.forename: R
authors.initials: R
authors.lastname: Gallego
authors.forename: C
authors.initials: C
authors.lastname: Parrado
authors.forename: M
authors.initials: M
authors.lastname: Blanco
authors.forename: V
authors.initials: V
authors.lastname: Bjornhagen
authors.forename: J
authors.initials: J
authors.lastname: Forteza
authors.forename: A
authors.initials: A
authors.lastname: Beiras
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000032:analysis*; D015266:Carcinoma, Merkel Cell / Q000378:metabolism* / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000556:secondary; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003937:Diagnosis, Differential; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018862:Merkel Cells / Q000378:metabolism*; D008875:Middle Aged; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule