Outcome and age distribution of cohort 1 FL patients (< 40 years of age). (A) Outcome of 27 cohort 1 FL patients (< 40 years of age). Patients with FL lacking BCL2 gene abnormality and with elevated Ki67 proliferation index (BCL2-N/HPI) demonstrated superior freedom from progression or relapse (median time not reached) compared with patients with FL bearing BCL2 gene rearrangement (BCL2-R) or nonelevated proliferation index (LPI; median, 41 months). (B) Age distribution of FL in patients < 40 (cohort 1).