Diffuse large B cell lymphoma expressing the natural killer cell marker CD56

The expression of the natural killer (NK) cell antigen, CD56, in hematologi cal malignancies is rare. However, there are several reports that some hema tological malignancies, such as T/NK cell lymphoma, multiple myeloma (MM) a nd acute myeloid leukemia (AML), express this molecule. In B cell non-Hodgk in's lymphomas (NHL), however, very limited number of cases have been repor ted to express CD56 molecule. Although one study has recently described tha t half of microvillous B cell lymphoma (MVL), an uncommon subset of large c ell lymphoma, expressed CD56, there have been no reports about most common type of B-NHL, diffuse large B cell lymphoma (DLBL) other than a mention of weak CD56 expression in one of 83 DLBL. We herein presented the first case of diffuse large B cell lymphoma expressing CD56 clearly. The immunophenot ype determined by immunostaining and flaw cytometric analysis was CD10(+), CD19(+), CD20(+), CD45RO(-), CD3(-) and CD56(+). On immunohistochemical stu dy, neither bcl-2 nor TIA-1 was positive for tumor cell. Monoclonal immunog lobulin heavy chain (IgH) gene rearrangement was detected, and the sequence analysis of the variable region of IgH OIH) suggested that this tumor was derived from antigen selected past germinal center B cell. Conventional com bination chemotherapy (CHOP) was administered, and the patient has still be en in complete remission for 10 months.