FLT3 and gastric cancer: Several potent small molecules were developed to selectively target tyrosine kinase receptors such as epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2) and FMS-like tyrosine kinase 3 (FLT3) which are overexpressed or constitutively activated in distinct types of cancer including breast cancer, lung cancer, bladder cancer, stomach cancer and acute myeloid leukemia (AML) [24, 33–36].