PIK3CD and acute lymphoblastic leukemia: IL7R signaling activates the JAK/STAT signaling and PI3K/Akt/mTOR pathways, which are among the histotype-specific driver alterations in leukemias [33], and is necessary for the normal development and maintenance of both B and T cells and crucial for leukemogenesis; activating gain-of-function mutations in IL7R have been well described in B-ALL.