CDKN2A and acute lymphoblastic leukemia: In particular, the COALL has proposed the IKZF1plus group, defined by the deletion of IKZF1 co-occurring with at least one additional deletion in CDKN2A/Bhomo, PAX5, or the pseudo autosomic region 1 (PAR1) in the absence of ERG deletion, which distinguishes high-risk ALL patients who benefit from treatment intensification [23].