Classical Hodgkin lymphoma primary refractory to brentuximab vedotin, with transformation to CD30-positive diffuse large B-cell lymphoma.

Brentuximab vedotin (BV) is an antibody-drug conjugate that targets CD30. It is highly effective for relapsed/refractory classical Hodgkin lymphoma (CHL), and has become a promising treatment option for these patients; however, approximately 25 % of patients are refractory to BV. Until now, the clinicopathologic features of CHL refractory to BV have not been well understood. Here, we report a patient with relapsed CHL with an unfavorable outcome, whose disease was primary refractory to BV and was histologically diagnosed as a transformation from mixed cellularity CHL to CD30-positive diffuse large B-cell lymphoma (DLBCL). The transformation to DLBCL showing high tumor density and high proliferative activity (Ki67 index >90 %) was possibly related to the primary refractory to BV and an aggressive clinical course, although the lymphoma was diffusely and strongly positive for CD30.