Chronic lymphocytic leukemia patients with IGH translocations are characterized by a distinct genetic landscape with prognostic implications

Chromosome 14q32 rearrangements/translocations involving the immunoglobulin heavy chain (IGH) are rarely detected in chronic lymphocytic leukemia (CLL). The prognostic significance of the IGH translocation is controversial and its mutational profile remains unknown. Here, we present for the first time a comprehensive next‐generation sequencing (NGS) analysis of 46 CLL patients with IGH rearrangement (IGHR‐CLLs) and we demonstrate that IGHR‐CLLs have a distinct mutational profile with recurrent mutations in NOTCH1, IGLL5, POT1, BCL2, FBXW7, ZMYM3, MGA, BRAF and HIST1H1E genes. Interestingly, BCL2 and FBXW7 mutations were significantly associated with this subgroup and almost half of BCL2, IGLL5 and HISTH1E mutations reported were previously identified in non‐Hodgkin lymphomas. Notably, IGH/BCL2 rearrangements were associated with a lower mutation frequency and carried BCL2 and IGLL5 mutations, while the other IGHR‐CLLs had mutations in genes related to poor prognosis (NOTCH1, SF3B1 and TP53) and shorter time to first treatment (TFT). Moreover, IGHR‐CLLs patients showed a shorter TFT than CLL patients carrying 13q−, normal fluorescence in situ hybridization (FISH) and +12 CLL, being this prognosis particularly poor when NOTCH1, SF3B1, TP53, BIRC3 and BRAF were also mutated. The presence of these mutations not only was an independent risk factor within IGHR‐CLLs, but also refined the prognosis of low‐risk cytogenetic patients (13q−/normal FISH). Hence, our study demonstrates that IGHR‐CLLs have a distinct mutational profile from the majority of CLLs and highlights the relevance of incorporating NGS and the status of IGH by FISH analysis to refine the risk‐stratification CLL model. What's new? The prognostic significance of the immunoglobulin heavy chain (IGH) translocation in chronic lymphocytic leukemia (CLL) is controversial and its mutational profile remains unknown. Here, the authors assessed for the first time the genetic landscape of CLL patients with IGH rearrangements by targeted next‐generation sequencing, characterising recurrently‐mutated genes with prognostic implications and demonstrating that these entities exhibit an intermediate mutational profile between CLL and non‐Hodgkin lymphoma. Moreover, the findings showed that the incorporation of next‐generation sequencing and the IGH‐probe in the CLL‐fluorescence in situ hybridisation panel used in clinical routine could be useful, especially for elucidating prognosis in normal FISH cases.