title: Primary central nervous system diffuse large B-cell lymphoma in the immunocompetent: Immunophenotypic subtypes and Epstein-Barr virus association.
abstract: BACKGROUND
  Primary central nervous system diffuse large B-cell lymphoma (PCNSL DLBCL) in the immunocompetent is an uncommon tumor that has an activated B-cell immunophenotype resembling germinal center exit B cells. They also differ from primary central nervous diffuse large B-cell lymphomas in the immunocompromised as they show no association with the Epstein-Barr virus.
  
  
  OBJECTIVE
  To determine if immunophenotypic subtyping of PCNS DLBCL from Asian subcontinent are also different similar to its systemic counterpart is unclear, as there are only limited studies from Asia, and none from India.
  
  
  METHODS
  The immunohistochemical profile of 24 South Indian patients with primary central nervous system diffuse large B-cell lymphoma was studied using germinal center markers - CD10 and Bcl-6, and activation markers - MUM1 and CD138, which are markers for late/post germinal centre B cells. Insitu hybridization for EBV genome and LMP1 by immunohistochemistry was carried out in all cases to determine association with EBV.
  
  
  RESULTS
  Centroblastic morphology and uniform activated B-cell phenotype with positivity for MUM1 was seen in 91.6% of tumors. Co-expression of Bcl-6 and MUM1 was evident in 50%, which is more frequent than in systemic diffuse large B-cell lymphomas. All cases were negative for Epstein-Barr virus using EBER in-situ hybridization and LMP1 immunohistochemistry.
  
  
  CONCLUSIONS
  Primary diffuse large B-cell lymphoma in the immunocompetent is a distinct clinicopathological entity with centroblastic morphology, a uniform activated B-cell immunophenotype that is not associated with the Epstein-Barr virus regardless of geographic origin.
authors.affiliation: Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India.
authors.forename: Anita
authors.initials: A
authors.lastname: Mahadevan
authors.affiliation: Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, Karnataka, India.
authors.forename: Clementina Rama
authors.initials: CR
authors.lastname: Rao
authors.affiliation: Department of Pathology, Kidwai Memorial Institute of Oncology, Bangalore, Karnataka, India.
authors.forename: M
authors.initials: M
authors.lastname: Shanmugham
authors.affiliation: Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India.
authors.forename: Susarla Krishna
authors.initials: SK
authors.lastname: Shankar
keywords: Activation markers; Epstein-Barr virus; MUM1; diffuse large B cell lymphoma; immunophenotype; primary central nervous system lymphoma