Correlation with CD79B expression and clinicopathological parameters including cell of origin, CD79A and CD19...

CD79B, the target of polatuzumab vedotin-an anti-CD79B antibody-drug conjugate-has shown greater efficacy in activated B-cell-type diffuse large B-cell lymphoma (DLBCL) than in germinal center B-cell (GCB) type. However, the correlation between CD79B expression and the clinicopathological parameters in DLBCL remains unknown. We evaluated CD79B expression using the H-score (range: 0-300) in 379 samples from 280 patients with DLBCL. Low CD79B expression (H-score ≤100) was observed in 48 samples (13 %), with 11 samples (3 %) showing no detectable expression. Notably, CD79B expression was significantly lower in the non-GCB type than in the GCB type (P < 0.001). Low CD79B expression correlated with advanced stage (P = 0.013), CD5 positivity (P = 0.014), and immunoblastic type (P = 0.067). Among the 48 DLBCL samples with low CD79B expression, 90 % demonstrated high (H-score >100) CD79A and CD19 expression. No mutation in the first tyrosine residue of CD79B immunoreceptor tyrosine-based activation motif, Y196, was identified in DLBCL with low CD79B expression. Additionally, low CD79B expression was not associated with the co-occurrence of CD79B ITAM and MYD88 L265P mutations (P = 0.748). Of the 78 patients with multiple biopsy specimens obtained from multiple sites or recurrent tumors, a change in CD79B expression from low to high or verse versa was observed in 9 % of patients. In conclusion, CD79B expression was lower in the non-GCB type than in the GCB type. CD79B, CD79A, and CD19 expressions were not completely correlated, and one expression cannot predict the others. In 9 % of patients, CD79B expression was inconsistent in multiple biopsy samples.