title: Relapsed angioimmunoblastic T-cell lymphoma with acquired expression of CD20: a case report and review of the literature.
abstract: BACKGROUND
  Angioimmunoblastic T-cell lymphoma is one of the most common types of peripheral T-cell lymphomas, usually presenting at an older age with an aggressive clinical course. Its characteristic morphological presentation and follicular helper T-cell phenotype help to distinguish it from other T-cell lymphomas.
  
  
  METHODS
  We recently encountered the unique case of a 63-year old patient with relapsed tumour-cell rich angioimmunoblastic T-cell lymphoma, presenting with a "classical" phenotype and, in addition, an acquired, strong, aberrant expression of CD20."Lineage infidelity" of phenotypic markers is a well-documented phenomenon in lymphomas and leukemias, a circumstance currently still poorly understood and with the potential to bring about erroneous interpretations, causing diagnostic havoc. This case represents one of the few documented angioimmunoblastic T-cell lymphomas with strong CD20 expression. Of interest, CD20 expression was only detected in the recurrent lymphoma and not upon initial diagnosis. The clinical importance of this finding lies in the potential for treatment with an anti-CD20 antibody, for instance Rituximab, in addition to standard chemotherapy protocols for angioimmunoblastic T-cell lymphoma.
  
  
  CONCLUSIONS
  Diagnostic work-up of lymphomas to determine their lineage should therefore consider morphology, pheno- as well as genotypic characteristics, where appropriate, and in particular signs of progression and change in marker profile in relapsed cases e.g. acquisition of "non-lineage" markers such as CD20 in T-cell lymphoma.
authors.affiliation: Institute of Pathology, University Hospital Basel, Schönbeinstrasse 4, 4031, Basel, Switzerland. aztankov@uhbs.ch.
authors.forename: Yara
authors.initials: Y
authors.lastname: Banz
authors.forename: Fatime
authors.initials: F
authors.lastname: Krasniqi
authors.forename: Stephan
authors.initials: S
authors.lastname: Dirnhofer
authors.forename: Alexander
authors.initials: A
authors.lastname: Tzankov