ZAP70 and B-cell chronic lymphocytic leukemia: Despite a remarkable phenotypic and cytological homogeneity, CLL is characterized by extremely variable clinical course related to different prognostic factors including the mutational status of the immunoglobulin heavy-chain variable region (IgVH) [2-4], expression of CD38 and ZAP70 markers [5, 6] and specific cytogenetic alterations [7-9].