Next-generation sequencing-based IG clonality analysis to discriminate reactive infiltrates from minimal lymphoma involvement in paired lymphoma and bone marrow biopsies: a EuroClonality-NGS Working Group study

Aims: 

Bone marrow (BM) biopsy is an important procedure in B-cell lymphoma staging. In most biopsies, the presence or absence of a lymphoma infiltrate can reliably be determined by standard histology. However, in a subset of cases with limited infiltration, this assessment remains inconclusive, requiring an alternative approach. Next-generation sequencing (NGS)-based detection of immunoglobulin (IG) gene rearrangements has the potential for resolving these difficult cases because of its high sensitivity. In this study, we tested the NGS-based IG clonality protocol developed by the EuroClonality-NGS Working Group on BM staging biopsies.

Methods and results: 

Forty-nine BM biopsies ranging from morphologically and immunohistochemically evidently involved to negative were analysed and compared to the original lymphoma. A clear distinction in the abundance of overlapping clonal IG rearrangements was observed between BM biopsies that were positive versus negative for lymphoma based on morphology and immunohistochemistry. In the 12 BM biopsies in which morphology and immunohistochemistry were insufficient to differentiate between the presence or absence of lymphoma, the estimated B-cell infiltration ranged from 1% to 5%. In these cases, NGS-based IG clonality analysis of paired primary lymphoma/BM biopsies provided a binary outcome; a subset of cases with hardly or no primary lymphoma-derived IG gene rearrangements in the BM biopsy could be distinguished from cases with clear presence of primary lymphoma-derived IG gene rearrangements. 

Conclusions: 

Our data demonstrated that paired NGS-based IG clonality analysis of lymphoma and BM samples can be a valuable additional tool for difficult BM staging biopsies in patients with B-cell lymphoma.