Receptor-type tyrosine-protein kinase FLT3 is involved in differentiation, proliferation, and survival of hematopoietic progenitor cells. Activating mutations of FLT3 are common in hematologic tumors. Simple variants in FLT3 are seen in about 15% of all cancers, including 20% of heme-related cancers and 5% of skin tumors. Certain FLT3 mutations may predict resistance to FLT3 inhibitors.