Following this strategy, a CLL sample is defined as ZAP-70 positive when at least 20% of CLL cells express ZAP-70 at levels comparable to those found in the residual T cell component [2,6] Given the different readouts utilized to define ZAP-70 positivity in CLL, it is not unexpected that a fraction of cases may result discordant when both approaches are applied to the same cohort of patients [7]. The gene discussed is ZAP70; the disease is B-cell chronic lymphocytic leukemia.