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Improved clonality assessment in germinal centre/post-germinal centre non-Hodgkin’s lymphomas with high rates of somatic hypermutation
  1. Mark A Catherwood1,
  2. David Gonzalez2,
  3. Caroline Patton3,
  4. Edwina Dobbin4,
  5. Lakshmi Venkatraman5,
  6. H Denis Alexander1
  1. 1Haemato-Oncology Laboratory, Belfast City Hospital, Belfast, Northern Ireland
  2. 2Department of Haemato-Oncology, BLB, Institute of Cancer Research, Surrey, UK
  3. 3Schools of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland
  4. 4Biological Sciences, University of Ulster, Coleraine, Northern Ireland
  5. 5Department of Histopathology, Royal Victoria Hospital, Belfast, Northern Ireland
  1. Correspondence to:
 Dr M A Catherwood
 Haemato-Oncology Laboratory, Department of Haematology, Level C, Belfast City Hospital, Belfast BT9 7AB, Northern Ireland; mark.catherwood{at}bll.n-i.nhs.uk

Abstract

Background: PCR detects clonal rearrangements of the Ig gene in lymphoproliferative disorders. False negativity occurs in germinal centre/post-germinal centre lymphomas (GC/PGCLs) as they display a high rate of somatic hypermutation (SHM), which causes primer mismatching when detecting Ig rearrangements by PCR.

Aims: To investigate the degree of SHM in a group of GC/PGCLs and assess the rate of false negativity when using BIOMED-2 PCR when compared with previously published strategies.

Methods: DNA was isolated from snap-frozen tissue from 49 patients with GC/PGCL (23 diffuse large B cell lymphomas (DLBCLs), 26 follicular lymphomas (FLs)) and PCR-amplified for complete (VDJH), incomplete (DJH) and Igκ/λ rearrangements using the BIOMED-2 protocols, and compared with previously published methods using consensus primers. Germinal centre phenotype was defined by immunohistochemistry based on CD10, Bcl-6 and MUM-1.

Results: Clonality detection by amplifying Ig rearrangements using BIOMED-2 family-specific primers was considerably higher than that found using consensus primers (74% DLBCL and 96% FL vs 69% DLBCL and 73% FL). Addition of BIOMED-2 DJH rearrangements increased detection of clonality by 22% in DLBCL. SHM was present in VDJH rearrangements from all patients with DLBCL (median (range) 5.7% (2.5–13.5)) and FL (median (range) 5.3% (2.3–11.9)) with a clonal rearrangement.

Conclusions: Use of BIOMED-2 primers has significantly reduced the false negative rate associated with GC/PGCL when compared with consensus primers, and the inclusion of DJH rearrangements represents a potential complementary target for clonality assessment, as SHM is thought not to occur in these types of rearrangements.

  • DLBCL, diffuse large B cell lymphoma
  • FL, follicular lymphoma
  • FR, framework
  • GC/PGCL, germinal centre/post-germinal centre lymphoma
  • SHM, somatic hypermutation

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Footnotes

  • Published Online First 30 June 2006

  • Competing interests: None declared.

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