CD117, also known as c-kit or SCF receptor, is a 145 kDa receptor tyrosine kinase involved in stem cell signaling, activation, and proliferation. The CD117 antigen is expressed on about 1–3% of peripheral blood mononuclear cells (PBMCs) and cord blood cells and on up to 10% of bone marrow cells. CD117 is further expressed on basophils, myeloid dendritic cells, TCRα/β+
T cells, CD19+
B cells, and CD56+
NK cells, as well as on mast cells, melanocytes, and acute myeloid leukemia (AML) blasts.