Aberrant phenotypic expression of the T-cell-associated antigen CD8 on B-cell chronic lymphocytic leukemia cells.

B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous hematologic malignancy caused by a clonally expanded B-cell population that recirculates between the blood and tissues. Described is the case of an 81-year-old female B-CLL patient with aberrant expression of a T-cell-associated antigen, CD8, on CD19+ B-CLL cells. Despite chlorambucil therapy and a subsequent salvage regimen, the patient rapidly entered progressive disease and died 9 months later. Flow cytometric immunophenotyping of the B-CLL cells for a number of antigens ruled out a mixed-lineage disorder. The implications of CD8 expression in B-CLL are discussed, and its expression in this case probably reflects an aberrant lineage infidelity. CD8 expression might be considered as a marker of aggressive disease.