Recent analysis has shown that copy number variations (CNVs) are common in ALL and leukemia in general, especially in genes involved in transcription, cell cycle regulation and B-cell differentiation, (e.g., CDKN2A/B, IKZF1, ETV6, EBF1, PAX5, BTG1 and PAR1) [4]. The gene discussed is BTG1; the disease is acute lymphoblastic leukemia.