Genetic characteristics of primary bone marrow large B-cell lymphoma

Primary bone marrow large B-cell lymphoma (PBM-LBCL) is a rare entity with poorly defined genetic features. We performed whole-exome sequencing on bone marrow specimens from 19 PBM-LBCL cases and compared them with 11 cases of conventional diffuse large B-cell lymphoma (DLBCL) with secondary bone marrow involvement. Clinicopathological characteristics, including hemophagocytic lymphohistiocytosis (HLH), hepatosplenomegaly, International Prognostic Index (IPI) score, treatment with chemotherapy plus rituximab, CD5 expression, histopathological patterns, germinal center B-cell-like subtype and follow-up duration, did not differ significantly between the two groups. Both IPI score and treatment regimen emerged as independent predictors of survival. Sequencing analysis revealed 7974 moderate- to high-impact variants. The MCD molecular subtype predominated in both cohorts, while the EZB subtype was observed exclusively in PBM-LBCL. A distinct 16-gene mutational signature differentiated PBM-LBCL from DLBCL. Among these, 10 genes (KMT2D, APOB, BBS9, CFAP46, EIF4G3, FAT1, MED12L, TG, TNR, ZFHX4) were uniquely mutated in PBM-LBCL, and three genes (CNTNAP3B, IL16, ZNF814) were exclusive to DLBCL. Mutations in COL5A3, PCNT, HMCN2, and OSBPL10 were associated with HLH. Notably, BTG1 mutation was significantly associated with poor prognosis in both univariate and elastic net-regularized multivariate analyses. In summary, PBM-LBCL harbors a distinct genetic profile, characterized by a unique 16-gene signature that distinguishes it from DLBCL with secondary bone marrow involvement. BTG1 mutation is associated with adverse outcomes, highlighting their potential as prognostic biomarkers or therapeutic targets. These findings advance our understanding of the molecular landscape and prognostic stratification of PBM-LBCL.