Composite diffuse large B‐cell lymphoma and CD20‐positive peripheral T‐cell lymphoma

Composite lymphoma is defined as two or more distinct types of lymphoma in a single anatomical site. Among various combinations, composite B‐cell and T‐cell non‐Hodgkin's lymphomas (CBTL) are very infrequent. Herein we describe a 66‐year‐old female with CBTL presenting with lymphadenopathy, multiple bone lesions and an epidural tumor. Light microscopic examination of a biopsied cervical node revealed a dual population of lymphoid cells: sheets of large cells admixed with medium‐sized cells. The large cells expressed B‐cell markers and showed immunoglobulin light chain restriction, consistent with diffuse large B‐cell lymphoma (DLBCL). The medium‐sized cells were positive for CD20 as well as T‐cell markers. Because polymerase chain reaction amplification showed monoclonal rearrangement of the T‐cell receptor β chain gene, this population was compatible with peripheral T‐cell lymphoma not otherwise specified (PTCL‐NOS). We therefore made a diagnosis of composite DLBCL and CD20‐positive PTCL‐NOS. Complete remission was achieved after six cycles of R‐CHOP regimen (rituximab, doxorubicin, vincristine, cyclophosphamide and prednisolone). This is the first report of CD20‐positive PTCL‐NOS associated with composite lymphoma. Moreover, a literature review of composite DLBCL and PTCL‐NOS indicates that this rare clinical entity may be featured by efficacy of systemic chemotherapy in spite of prevalent extranodal lesions.