Higher TCL1 expression is associated with higher WBC and predicts poor clinical outcome, regardless of treatment. (A) Median and range of WBC at diagnosis in all 70 patients were significantly higher in CLLs with moderate or strong TCL1 expression compared with the TCL1-dim/negative cases. (B) Among untreated patients, CLL cases that strongly expressed TCL1 developed higher peak WBCs. (C) Higher TCL1 levels correlated with shorter PFS among all 59 treated patients and (D) with shorter OS in all 70 cases studied in culture. (E) PFS was shorter for patients with high-level TCL1 carrying tumors for both the 34 cases treated upfront with 1- or 2-drug fludarabine-containing regimens and (F) for the 22 cases treated with frontline 3- or 4-drug chemo-immunotherapy regimens.