OBJECTIVETo report the diagnosis, differential diagnosis and treatment of a rare case of primary bone marrow CD8+ cytotoxic T-cell lymphoma coexpressed CD20.

METHODSThe clinical characteristics, therapeutic course and the outcome of this patient were reviewed. Meanwhile, a series of examinations including morphology, flow cytometry, immunohistochemistry and molecular biology of bone marrow and skin samples were also performed.

RESULTSBone marrow biopsy showed an extensive involvement by abnormal T lymphocytes. Flow cytometry and immunohistochemistry showed weakly positive CD20, CD8(+), CD2(+), CD3(+), CD5(+), TIA(+), PAX-5(-), CD4(-), CD56(-), CD57(-), CD30(-), ALK-1(-), P53(-), TdT(-), Ki-67≈5%. A final diagnosis of primary bone marrow CD8+ cytotoxic T-cell lymphoma coexpressed CD20 was made. The patient initially presented a relatively indolent course was, but he was expired in the end 3 years later due to extensive involvements of skin and other organs though timely therapy was administrated.

CONCLUSIONPrimary bone marrow CD8 cytotoxic T-cell lymphoma coexpressed CD20 was encountered rarely in clinical practice, which might be a challenging in terms of diagnosis and differential diagnosis. Further investigation of pathogenesis and therapeutic strategies of this rare disease was warranted.