PD-L1 Expression and Tumor Microenvironment Dynamics in Diffuse Large B-Cell Lymphoma: Immunophenotypic Insights

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of B-cell non-Hodgkin lymphoma (NHL) and is characterized by significant biological and clinical heterogeneity.The programmed death 1 (PD-1)/ programmed death-ligand 1 (PD-L1) immune checkpoint pathway plays a crucial role in tumor immune evasion; however, its diagnostic and prognostic relevance in DLBCL remains unclear.We retrospectively analyzed 66 cases of DLBCL diagnosed between 2017 and 2024 at a single institution.Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissues using antibodies against PD-L1, PD-1, CD4, CD8, and CD68.Clinical data and histopathological features were correlated with marker expression.Statistical analyses were conducted using IBM SPSS 25, with a significance level set at P < 0.05.PD-L1 expression (greater than 1%) in tumor cells was infrequent (6/66 cases), while immune cell PD-L1 positivity was prevalent (39/66 cases).PD-1 positivity was observed in five tumor samples and 40.9% of stromal immune cells.A significant association was found between tumoral PD-L1 expression and histological subtype (P = 0.015), with anaplastic variants showing higher expression levels.Positive PD-1 expression in immune cells was significantly associated with female gender (P = 0.044).High CD68 expression correlated with a lower Ann Arbor stage (P = 0.040) and tumor morphology (P = 0.010).CD4 and CD8 expression levels showed no significant correlations with clinicopathological features.PD-L1 and PD-1 expression patterns in DLBCL highlight their potential relevance for immune evasion and prognosis, particularly in anaplastic variants.The tumor microenvironment, especially macrophage infiltration, plays a complex role in disease progression.Further studies are needed to validate these findings and investigate therapeutic implications.