Primary testicular diffuse large B-cell lymphoma shows an activated B-cell-like phenotype

The most common type of primary testicular lymphoma is diffuse large B-cell type, which has a poor prognosis relative to other extra-nodal diffuse large B-cell lymphomas (DLBCL). These constitute a heterogeneous group of lymphomas with germinal center B-cell-like and activated B-cell-like subtypes. Such a distinction theoretically utilizes the immunohistochemical expression of CD10, Bcl-6, and MUM1. The purpose of this study was that we could stratify primary testicular lymphoma of diffuse large B-cell type according to this scheme, and further elucidate the reason why primary testicular diffuse large B-cell lymphoma possesses a poor clinical outcome. Seventeen Chinese patients with primary testicular DLBCL were examined by means of a 3-antibody panel (CD10, Bcl-6, MUM1). Among these 17 cases, 16 were assigned to the activated B-cell-like subtypes. One case was classified as germinal center B-cell-like type. Twelve of these 17 cases expressed high proliferative activity (>or=40% Ki-67 labeling). The majority of primary testicular DLBCLs have activated B-cell-like subtype characteristics and high proliferative activity. These features might be a significant factor; moreover, they are associated with poor prognosis.