Schematic depicting structure of receptor tyrosine kinase type III family. Structure of receptor tyrosine kinase type III family, on the left, shows 5 immunoglobulin-like ligand-binding domains (JM indicates the juxtamembrane domain) and two split kinase domains. FLT3 receptor has mutations identified in the JM as well as in the second split kinase domain at codon 835. c-KIT has a mutation in the immunoglobulin extracellular domain at a highly conserved aspartate residue at codon 419 as well as in the split kinase domain at codon 816, which is frequently seen in mast cell leukemia or mastocytosis.