Monoclonal expansion of large granular lymphocytes with a CD4+ CD8dim+/- phenotype associated with hairy cell leukemia.

Peripheral blood lymphoid cell expansions with an unusual CD3+, CD4+, CD8dim+/-, CD11b+, CD57+ immunophenotype have recently been reported. They frequently have the morphology of large granular lymphocytes (LGL) and can be either monoclonal or polyclonal. Their significance is still unclear and no association with hematological neoplasms has been described. We report the case of a patient with a monoclonal expansion of LGL associated with a B-cell-derived hairy cell leukemia. The two lymphoid clones were not physically associated since T-LGL were found in the peripheral blood and hairy cells were detected in the bone marrow and kidney.