Probes for INS

Primary mediastinal large B-cell lymphoma (PMLBCL) is recognized as a distinct clinicopathological entity in the current World Health Organization classification of lymphoid neoplasms (Swerdlow et al, 2016). Gene expression profiling studies have confirmed a distinct signature in PMLBCL that differs from diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS) and partially overlaps with that found in classical Hodgkin lymphoma (Savage et al, 2003; Bea et al, 2005). In routine clinical practice, however, distinguishing between PMLBCL and DLBCL, NOS is frequently difficult, due partly to a paucity of sensitive and specific biomarkers (Martelli et al, 2008; Dorfman et al, 2012). Recent studies have shown that PMLBCL shows frequent copy number alterations or translocations involving the CD274 (PD-L1) or PDCD1LG2 (PD-L2) genes at chromosome 9p24.1, leading to overexpression of CD274 (PD-L1) and, especially, PDCD1LG (PD-L2) proteins (Shi et al, 2014; Twa & Steidl, 2015). Anti-PDCD1LG2 antibodies suitable for immunohistochemical analysis in formalin-fixed paraffin-embedded (FFPE) tissue are not currently commercially available, limiting the utility of this potential marker for routine diagnostic practice. In this study, we have performed RNA in situ hybridization (RISH) for CD274 and PDCD1LG2 RNA expression, using a standard automated immunohistochemistry (IHC) platform, and have compared the results to IHC using a commercially available anti-CD274 antibody.