[CD20-positive peripheral T-cell lymphoma, not otherwise specified].

We report a 69-year-old male with CD3-positive peripheral T-cell lymphoma, not otherwise specified (PTCL-nos). Interestingly, tumor cells slightly expressed CD20 as well. Southern analyses of the tumor cells showed rearrangement for only the T cell receptor gene but not the immunoglobulin genes. This patient achieved partial remission with a treatment regimen of THP-COP excluding prednisolone, but died of pneumonia. Although CD20-positive PTCL is rare, a review of the reported cases suggests that CD20-positive PTCL has a poor prognosis and that bone marrow infiltration of tumor cells results in a poorer prognosis in CD20-positive PTCL than in usual PTCL. By accumulating cases of this rare entity of lymphoma, we need to clarify the biological nature of the tumor cells and usefulness of rituximab combined with standard chemotherapy.