Aberrant expression of the CD8 antigen in B cell chronic lymphocytic leukaemia

We report a case of aberrant expression of the T cell antigen CD8 in a patient with B cell chronic lymphocytic leukaemia (B-CLL). A 62-year-old Caucasian female with several enlarged lymph nodes and suspected to have B-CLL was referred to our laboratory for routine immunophenotyping. Peripheral blood cell count showed moderate leucocytosis without other abnormalities. The dual-colour flow cytometric analysis showed a typical B-CLL phenotype (CD45 +, CD19 +, kappa+, lambda-, CD20 +, CD23 +, IgM +, HLA-DR +, CD5/CD19 +, CD3 -). In addition, aberrant expression of the T cell marker CD8 was found, present on approximately 64% of the leukemic cells. This is a rare even, the significance and nature of this aberration has not yet been fully determined. In this case, our patient had a rapid response to treatment with a remarkable reduction in the number of leukemic cells only two weeks after beginning treatment.