# 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

## TL;DR

NGS-based immunoglobulin clonality analysis helps distinguish lymphoma from normal cells in bone marrow biopsies when traditional methods are unclear.

## Contribution

Paired NGS-based IG clonality analysis of lymphoma and bone marrow samples improves staging accuracy in B-cell lymphoma.

## Key findings

- NGS detected lymphoma-derived IG rearrangements in bone marrow with 1-5% B-cell infiltration.
- Paired analysis provided a binary outcome for ambiguous cases.
- Results showed a clear distinction between positive and negative lymphoma cases.

## Abstract

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.

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.

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.

Next‐generation sequencing (NGS) immunoglobulin clonality analysis can help resolve ambiguous bone marrow staging biopsies for B‐cell lymphoma. In this study, paired analysis of the primary lymphoma and bone marrow helped to detect lymphoma involvement in cases with inconclusive morphology and immunohistochemistry, making it a valuable tool for difficult staging biopsies.