PD-L1 (SP142) expression in neoplastic cells predicts a poor prognosis for patients with intravascular large B-cell lymphoma treated with rituximab-based multi-agent chemotherapy.

Background: Intravascular large B-cell lymphoma (IVLBCL) is a rare form of diffuse large B-cell lymphoma (DLBCL) arising in extranodal sites. PD-L1 expression of tumor cells has been reported in IVLBCL cells, but its clinicopathological relevance remains to be elucidated.

Aims: This study was aimed to reveal the characteristics of PD-L1+ IVLBCL. Methods and

Results: Neoplastic PD-L1 expression was examined in 34 cases of IVLBCL and clinicopathological characteristics between patients with PD-L1+ and PD-L1- IVLBCL were compared. We assessed PD-L1 expression with SP142 antibody. Twelve (35%) of 34 cases showed positivity for PD-L1. The PD-L1+ group had significantly lower survival rates compared to the PD-L1- group. The PD-L1+ IVLBCL group also had a significantly lower age distribution and a lower frequency of patients older than 60 years compared to the PD-L1- group. Very recently, we speculate that there is possible link between PD-L1+ IVLBCL and PD-L1+ extranodal DLBCL-NOS (eDLBCL) because features of the two groups showed overlapping. Therefore, we compared the clinicopathological characteristics of the PD-L1+ IVLBCL and PD-L1+ eDLBCL. There were no significant differences in clinicopathological parameters and prognosis.

Conclusion: The worse prognosis of the PD-L1+ group might be caused by immune evasion mechanisms, which are linked to PD-L1 expression. Therefore, PD-L1+ IVLBCL cases might be regarded as good candidates for targeted immunotherapy. We also highlighted the overlapping features of PD-L1+ IVLBCL and PD-L1+ eDLBCL. This result suggests that they should be regarded as one entity, immune evasion-related extranodal large B-cell lymphoma.