Diagnostic utility of programmed cell death ligand 1 (clone SP142) immunohistochemistry for malignant lymphoma and lymphoproliferative disorders: A brief review
Ayako Sakakibara, Kei Kohno, Eri Ishikawa, Yuka Suzuki, Yuta Tsuyuki, Satoko Shimada, Kazuyuki Shimada, Akira Satou, Taishi Takahara, Akiko Ohashi, Emiko Takahashi, Seiichi Kato, Shigeo Nakamura, Naoko Asano
Ayako Sakakibara
Department of Pathology and Laboratory Medicine, Nagoya University Hospital, Nagoya, Japan,
Yuta Tsuyuki
Satoko Shimada
Department of Hematology and Oncology, Nagoya University Graduate School of Medicine, Nagoya, Japan,
Department of Surgical Pathology, Aichi Medical University Hospital, Nagakute, Japan,
Taishi Takahara
Department of Pathology and Molecular Diagnostics, Aichi Cancer Center Hospital,
Department of Clinical Laboratory, Nagano Prefectural Suzaka Hospital, Nagano, Japan
キーワード: programmed cell death 1 ligand 1,	classic Hodgkin lymphoma,	diffuse large B-cell lymphoma,	immune escape,	immunodeficiency	
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.