Among the genetic aberrations observed in T-ALL, there are lesions occurring commonly in many other cancers (e.g., inactivating mutations and deletions of PTEN and TP53 genes, activating gene mutations of the JAK-STAT pathway) as well as T-ALL-specific lesions, mainly affecting transcription factors crucial for normal differentiation of T-cell precursors (e.g., BCL11B, TAL1, TAL2, LYL1). The gene discussed is PTEN; the disease is acute lymphoblastic leukemia.