Differential Expression of CD79B, CD19, and PD‐L1 in de Novo and Transformed CD20‐Negative Large B‐Cell Lymphomas

ABSTRACT CD20‐negative large B‐cell lymphomas exhibit aggressive behavior and are ineligible for rituximab‐containing therapy. To identify antigens targeted by treatment, we analyzed CD79B and CD19 expression in 108 samples from 75 patients with CD20‐negative large B‐cell lymphomas using H‐score. Diffuse‐strong (H‐score 300) CD79B and CD19 expression was observed in 51% and 57% of samples, and low/negative (H‐score ≤ 100) in 35% and 30%, respectively. CD79B expression was significantly lower in de novo CD20‐negative diffuse large B‐cell lymphoma (DLBCL) than in CD20‐negative DLBCL changed from CD20‐positive DLBCL after rituximab‐containing therapy and in CD20‐negative DLBCL transformed from CD20‐positive low‐grade B‐cell lymphoma after rituximab‐containing therapy (H‐score ≤ 100 in 79% vs. 27% vs. 10%, p < 0.001). CD19 expression was lower in de novo CD20‐negative DLBCL than in transformed DLBCL (H‐score ≤ 100 in 43% vs. 3%, p = 0.006). Of 12 patients with plasmablastic lymphoma, CD79B and CD19 were negative in 83% and 66% of cases, respectively. Among 46 CD20‐negative large B‐cell lymphomas with low CD79B and/or CD19 expression, the tumor proportion score for programmed death‐ligand 1 was positive (≥ 1%) in 33% of cases. The combined positive score for programmed death‐ligand 1 was positive in 52% of programmed death‐ligand 1 tumor proportion score‐negative samples. In conclusion, CD79B and CD19 were variably expressed in CD20‐negative large B‐cell lymphomas, but lower in de novo DLBCL, and especially in plasmablastic lymphoma. Programmed cell death protein 1/programmed death‐ligand one inhibitors may represent a treatment option.