The presence of MCL-1 dependence in CD8+ T-LGLL cases is variable and not compulsory associated with mutated STAT3. In our heterogeneous series of T-LGLL cases, functional BH3 profiling identified cases of CD8+ T-LGLL with enhanced MCL1 dependence and sensitivity to the MCL1 inhibitor AZD5991 as compared to the same patient’s CD4+ T-cells. The gene discussed is MCL1; the disease is T-cell large granular lymphocyte leukemia.