Clonal Complexity Defines Distinct Tumor‐Intrinsic Biology and Prognosis in Diffuse Large B‐Cell Lymphoma

Background Intratumor heterogeneity (ITH), characterized by the coexistence of genetically distinct subclones within a tumor, has been associated with adverse clinical outcomes in various cancers. However, the clinical and biological implications of ITH in diffuse large B‐cell lymphoma (DLBCL) are still incompletely understood. Materials & Methods In this study, we applied a SNP‐array–based approach to assess the clonal complexity in formalin‐fixed, paraffin‐embedded tumor specimens obtained from newly diagnosed patients with advanced‐stage DLBCL ( n = 74) by calculating the clonal composition (CC) number. Rseults Patients with Poly‐CC tumors (CC ≥ 1), which accounted for 79.7% of the cases, had a 5‐year event‐free survival rate of 38.9%, compared with 69.1% in those with Mono‐CC tumors (CC = 0) (Log‐rank p = 0.0520). This association reached statistical significance in the activated B‐cell (ABC) subtype ( n = 35, Log‐rank p = 0.0450) but not in the germinal center B‐cell (GCB) subtype ( n = 30, Log‐rank p = 0.910). Gene set enrichment analysis revealed upregulation of cell cycle–related pathways in Poly‐CC tumors, consistent with the significantly higher Ki‐67 positivity rate than in Mono‐CC tumors, as confirmed by immunohistochemistry ( p = 0.00227). Within the ABC subtype, Poly‐CC (Poly‐ABC) tumors exhibited more differentiated transcriptional states and enrichment of IRF4‐associated gene signatures as compared with Mono‐CC (Mono‐ABC) tumors. Conversely, IFN‐γ and IFN‐α response pathways and the IL‐6/JAK‐STAT3 signaling pathway were markedly suppressed in the Poly‐ABC tumors. Furthermore, Poly‐ABC tumors carried a significantly higher number of pathogenic mutations as compared with Mono‐ABC tumors ( p = 0.0147). Conclusion These results suggest that clonal complexity captures tumor‐intrinsic features and biological diversity in DLBCL, especially in the ABC subtype, offering novel insights into the disease pathogenesis.