According to biologic features, there is a substantial "gray zone" between nodular lymphocyte predominant Hodgkin lymphomas (NLPHLs) (Poppema lymphomas) and T-cell/histiocyte-rich B-cell lymphomas (T/HRBCLs). Transformation from an NLPHL to a T/HRBCL can occur and is associated with a worsening of the prognosis. Here is described a case of a 16-year-old boy who presented with an NLPHL with features of T/HRBCL. Clinical evolution was complicated by 2 relapses leading to autologous and then to allogeneic bone marrow transplantation.