title: ERG expression in multiple myeloma-A potential diagnostic pitfall.
abstract: BACKGROUND
  ERG expression has been described as a frequent event in prostate cancer indicating poor prognosis and promoting oncogenesis. It has also been demonstrated in Ewing's sarcoma, acute myeloid leukemia and acute T-lymphoblastic leukemia but could not be found in other epithelial tumors, Hodgkin's or Non-Hodgkin's lymphoma. We aimed to analyze ERG expression in multiple myeloma, following an index case of a patient with metastases of unknown origin in the spine strongly expressing ERG, which were thought to be of prostatic origin but turned out to be plasmacytic lesions.
  
  
  METHODS
  We subsequently selected 12 formalin-fixed, paraffin-embedded tissue samples of multiple myeloma from our archives and performed immunohistochemical staining for ERG.
  
  
  RESULTS
  All 12 analyzed cases showed strong nuclear expression of ERG in >90% of tumor cells (myeloma cells).
  
  
  CONCLUSIONS
  This report highlights a potential and critical diagnostic pitfall in biopsy specimens where morphology is only of limited assistance in reaching the correct diagnosis. It urges pathologists to exercise caution in cases where strong ERG-positivity implicates the presence of a prostatic neoplasia and illustrates the need for further immunohistochemical examination.
authors.affiliation: Department of Pathology, Section of Hematopathology and Endocrine Pathology, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany. Electronic address: Juliana.Knief@uksh.de.
authors.forename: Juliana
authors.initials: J
authors.lastname: Knief
authors.affiliation: Department of Pathology, Section of Hematopathology and Endocrine Pathology, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Reddemann
authors.affiliation: Department of Neurosurgery, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Gliemroth
authors.affiliation: Department of Internal Medicine I, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
authors.forename: Swantje
authors.initials: S
authors.lastname: Brede
authors.affiliation: Department of Internal Medicine I, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bartscht
authors.affiliation: Department of Pathology, Section of Hematopathology and Endocrine Pathology, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Thorns
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D010954:Plasmacytoma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D013125:Spinal Neoplasms / Q000378:metabolism / Q000556:secondary* / Q000601:surgery; D013904:Thoracic Vertebrae; D000071230:Transcriptional Regulator ERG / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; C072312:ERG protein, human; D000071230:Transcriptional Regulator ERG
keywords: ERG expression; Multiple myeloma; Plasmacytoma