Molecular Fingerprinting of Anatomically and Temporally Distinct B-Cell Lymphoma Samples by Next-Generation Sequencing to Establish Clonal Relatedness

Abstract

Context.— B-cell lymphomas exhibit balanced translocations that involve immunoglobulin loci and result from aberrant V(D)J recombination, class switch recombination, or somatic hypermutation. Although most of the breakpoints in the immunoglobulin loci occur in defined regions, those in the partner genes vary; therefore, it is unlikely that 2 independent clones would share identical breakpoints in both partners. Establishing whether a new lesion in a patient with history of lymphoma represents recurrence or a new process can be relevant. Polymerase chain reaction (PCR)–based clonality assays used in this setting rely only on evaluating the length of a given rearrangement. In contrast, next-generation sequencing (NGS) provides the exact translocation breakpoint at single-base resolution. Objective.— To determine if translocation breakpoint coordinates can serve as a molecular fingerprint unique to a distinct clonal population. Design.— Thirty-eight follicular lymphoma/diffuse large B-cell lymphoma samples collected from different anatomic sites and/or at different time points from 18 patients were analyzed by NGS. For comparison, PCR-based B-cell clonality and fluorescence in situ hybridization studies were performed on a subset of cases. Results.— IGH-BCL2 rearrangements were detected in all samples. The breakpoint coordinates on derivative chromosome(s) were identical in all samples from a given patient, but distinct between samples derived from different patients. Additionally, 5 patients carried a second rearrangement also with conserved breakpoint coordinates in the follow-up sample(s). Conclusions.— Breakpoint coordinates in the immunoglobulin and partner genes can be used to establish clonal relatedness of anatomically/temporally distinct lesions. Additionally, an NGS-based approach has the potential to detect secondary translocations that may have prognostic and therapeutic significance.