Expression pattern of PD ‐L1 and PD ‐L2 in classical Hodgkin lymphoma, primary mediastinal large B‐cell lymphoma, and gray zone lymphoma

Objectives We aimed at investigating the relationship between classical Hodgkin lymphoma ( cHL ), primary mediastinal large B‐cell lymphoma ( PMBL ), and gray zone lymphoma ( GZL ) with intermediate characteristics between cHL and PMBL , from the perspective of the aberration in programed cell death 1 and the programed death ligands ( PDL s) network. Methods We explored the expression levels of PDL s and chromosomal anomalies in 67 cases: 34 cases with cHL , 20 with PMBL , and 13 with GZL , using immunohistochemical analyses and Fluorescence In Situ Hybridization ( FISH ). Results Twenty‐one cHL (62%), 3 PMBL (15%), and 6 GZL (46%) cases showed staining to PD ‐L1 antibodies in more than 70% of tumor cells. Two cHL (6%), 10 PMBL (50%), and 3 GZL (23%) cases were not stained by PD ‐L1 antibodies. Patients over 40 years old manifest more frequent expression of PD ‐L1 in cHL . Proportion of tumors stained by PD ‐L2 antibody was increased in PMBL . FISH analyses with a PD ‐L1/ PD ‐L2 probe detected 5 amplification, 1 gain, and 7 polysomy cases in cHL , 1 amplification and 1 polysomy case in GZL , and amplification in 1 PMBL case. Conclusion We identified increased staining of PD ‐L1 in cHL and that of PD ‐L2 in PMBL . GZL had a pattern similar to that of cHL .