MTOR and cancer: PIK3CA mutations frequently occur in diverse cancers and are associated with constitutive activation of the PI3K/AKT/mTOR pathway.[1-5] In addition, PIK3CA mutations predicted sensitivity to PI3K/AKT/mTOR inhibitors in multiple tumor types in preclinical and early clinical experiments.[1, 2, 5-12] A seminal question is whether PIK3CA mutations are associated with a distinct phenotypic taxonomy.