Immunohistochemistry as a valuable tool to assess CD30 expression in peripheral T-cell lymphomas: high correlation with mRNA levels

The extended use of Brentuximab-Vedotin was reported for CD30+ non-anaplastic peripheral T-cell lymphomas (PTCLs) with promising efficacy. CD30 status assessment is thus a critical factor for therapeutic decision, but the reliability of immunohistochemistry in evaluating its expression remains to be defined. This prompted us to investigate the correlation between semi-quantitative CD30 protein assessment by immunohistochemistry and mRNA assessment by microarrays, in a cohort of 376 non-cutaneous PTCLs representative of the main entities. By immunohistochemistry, CD30 expression was heterogeneous across and within entities, and significantly associated with large tumor cell size. In addition to 100% anaplastic large cell lymphomas, 57% of other PTCL entities were CD30-positive at a 5% threshold. CD30 protein expression was highly correlated to mRNA levels. mRNA levels were bimodal, separating high from low CD30-expressing PTCL cases. We conclude that immunohistochemistry is a valuable tool in clinical practice to assess CD30 expression in PTCLs.