Diagnostic utility of programmed cell death ligand 1 (clone SP142) immunohistochemistry for malignant lymphoma and lymphoproliferative disorders: A brief review

• Published in: Journal of Clinical and Experimental Hematopathology Vol. 61; no. 4; pp. 182 - 191
• Main Authors: Sakakibara, Ayako, Kohno, Kei, Ishikawa, Eri, Suzuki, Yuka, Tsuyuki, Yuta, Shimada, Satoko, Shimada, Kazuyuki, Satou, Akira, Takahara, Taishi, Ohashi, Akiko, Takahashi, Emiko, Kato, Seiichi, Nakamura, Shigeo, Asano, Naoko
• Format: Journal Article
• Language: English; Japanese
• Published: Japan The Japanese Society for Lymphoreticular Tissue Research 01.01.2021; JSLRT
• Subjects: Adult; Apoptosis; B7-H1 Antigen; Biomarkers, Tumor; classic Hodgkin lymphoma; Clone Cells; diffuse large B-cell lymphoma; Humans; immune escape; immunodeficiency; Immunohistochemistry; Ligands; Lymphoma, Large B-Cell, Diffuse - diagnosis; Lymphoproliferative Disorders; programmed cell death 1 ligand 1; immune escape; immunodeficiency; diffuse large B-cell lymphoma; classic Hodgkin lymphoma; programmed cell death 1 ligand 1
• ISSN: 1346-4280; 1880-9952
• DOI: 10.3960/jslrt.21003

The programmed cell death 1 (PD1)/PD1 ligand (PD-L1) axis plays an important role in tumor cell escape from immune control and has been most extensively investigated for therapeutic purposes. However, PD-L1 immunohistochemistry is still not used widely for diagnosis. We review the diagnostic utility of PD-L1 (by clone SP142) immunohistochemistry in large-cell lymphomas, mainly consisting of classic Hodgkin lymphoma (CHL) and diffuse large B-cell lymphoma (DLBCL). Neoplastic PD-L1 (nPD-L1) expression on Hodgkin and Reed-Sternberg cells is well-established among prototypic CHL. Of note, EBV+ CHL often poses a challenge for differential diagnosis from peripheral T-cell lymphoma with EBV+ non-malignant large B-cells; their distinction is based on the lack of PD-L1 expression on large B-cells in the latter. The nPD-L1 expression further provides a good diagnostic consensus for CHL with primary extranodal disease conceivably characterized by a combined pathogenesis of immune escape of tumor cells and immunodeficiency. Compared with CHL, the nPD-L1 expression rate is much lower in DLBCL, highlighting some specific subgroups of intravascular large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and EBV+ DLBCL. They consist of nPD-L1-positive and -negative subgroups, but their clinicopathological significance remains to be elucidated. Microenvironmental PD-L1 positivity on immune cells may be associated with a favorable prognosis in extranodal DLBCL. PD-L1 (by SP142) immunohistochemistry has helped us to understand the immune biology of lymphoid neoplasms possibly related by immune escape and/or immunodeficiency. However, knowledge of these issues remains limited and should be clarified for diagnostic consensus in the future.