Differences in mutational signature of diffuse large B‐cell lymphomas according to the primary organ

Abstract Background Comprehensive molecular subtyping of diffuse large B‐cell lymphoma (DLBCL) through genetic profiling has broadened our understanding of DLBCL biology. In this study, we investigated whether DLBCL, not otherwise specified (NOS) shows differences in mutational patterns depending on the primary organ. Patients and Methods Panel‐based next‐generation sequencing was performed on 345 DLBCL from various primary organs, and patterns of mutations according to primary organs were analyzed. Results DLBCL showed a characteristic mutational signature in several primary organs. Among them, the mutational pattern of DLBCL in the breast and ileocecal area was particularly different from that of other DLBCL NOS. In breast DLBCL, MYD88L265P (57.1%), CD79B mutation (42.9%), and CDKN2A/B loss (71.4%) were found at high frequencies, which were similar to the mutation patterns of DLBCL of immune‐privileged sites compared with DLBCL NOS. DLBCL in the ileocecal area showed a characteristic mutation pattern with the most frequent TP53 mutation (52.6%) and 18q21 gain (42.1%). This was also different from the mutational pattern observed in the stomach or other intestines. In discriminant analysis, DLBCL of the breast and ileocecal area tended to form separate genetic constellations from other DLBCL NOS. Conclusion DLBCL NOS has a characteristic mutational profile that depends on the primary organ. In particular, the mutational signature of DLBCL in the breast and ileocecal area was heterogeneous compared with that of other DLBCL NOS. Further research is needed to determine whether primary DLBCL in the breast and ileocecal area can be classified as an independent subtype.