It is broadly expressed by mature B-cells, and has also been found on a majority of chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), hairy cell leukemia (HCL), and mantle cell lymphoma (MCL) cells [11–13]; therefore, FCRL1 may be a potential target for immunotherapy of B-cell disorders. This evidence concerns the gene FCRL1 and hairy cell leukemia.