title: PAX8 and PAX5 are differentially expressed in B-cell and T-cell lymphomas.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the expression patterns of B-cell specific activator protein (BSAP)/PAX5 and PAX8 in a wide variety of B-cell and T-cell neoplasms.
  
  
  RESULTS
  A wide range of B-cell and T-cell neoplasms were subjected to immunohistochemical staining with antibodies against BSAP/PAX5 and PAX8 (polyclonal, pPAX8; monoclonal, mPAX8). Ten non-neoplastic lymph node specimens were examined with the same panel. All of the tested neoplastic and non-neoplastic B-cells reacted with the BSAP/PAX5 and pPAX8 antibodies, but did not show reactivity with the mPAX8 antibody. All tested T-cell neoplasms were negative using the BSAP/PAX5, pPAX8 and mPAX8 antibodies.
  
  
  CONCLUSIONS
  This is the first study to show the absence of reactivity to an mPAX8 antibody in an expanded panel of B-cell lymphomas as well as in a variety of T-cell neoplasms. In contrast to the mPAX8 antibody, the pPAX8 antibody shows nuclear positivity in non-neoplastic B cells and mature B-cell neoplasms; however, this expression is probably a result of cross-reactivity with PAX5. Given that many laboratories use the pPAX8 antibody, a clear understanding of the differential staining patterns is necessary. The differential diagnosis of a B-cell lymphoma should be entertained when a pPAX8-positive, epithelial marker-negative neoplasm of uncertain primary origin is encountered.
authors.affiliation: Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Morgan
authors.forename: Olga
authors.initials: O
authors.lastname: Pozdnyakova
authors.forename: Alessandra F
authors.initials: AF
authors.lastname: Nascimento
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Hirsch
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D016393:Lymphoma, B-Cell / Q000175:diagnosis / Q000378:metabolism*; D016399:Lymphoma, T-Cell / Q000175:diagnosis / Q000378:metabolism*; D051757:PAX5 Transcription Factor / Q000032:analysis / Q000096:biosynthesis*; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D014408:Biomarkers, Tumor; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors