We found dim to moderate BAFF-R expression in 54% (13/24) of B-ALL cases. Patients who have failed prior blinatumomab show a higher percentage of cases with BAFF-R positivity compared to newly diagnosed patients (11/17, 65% vs 2/7, 29%)….Expression of BAFF-R is important to detect as it can be therapeutic target for CAR T-cells or other immunotherapies and would benefit patients who have relapsed/refractory disease that have failed anti-CD19 therapy.