AFF1 and acute lymphoblastic leukemia: In 184 adult patients with pro-B CD10neg ALL enrolled in two consecutive clinical trials (GMALL 6/99 and 7/03), MLL-AF4 positive patients were characterized by a more aggressive clinical presentation, with higher WBC at diagnosis (median: 141 × 109/L), but no difference was reported for age at presentation between MLL/AF4 positive and negative patients [7].