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

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.