Test Details: The CD117 protein is a transmembrane, tyrosine kinase growth factor receptor. It is present in a variety of normal human cell types, including breast epithelium, germ cells, melanocytes, immature myeloid cells, and mast cells. The CD117 ligand is stem cell factor, an important hematopoietic regulator. CD117 is present on approximately 4% of normal bone marrow mononuclear cells and in acute myelogenous leukaemia (AML) and chronic myelogenous leukaemia in myeloid blast crisis. CD117 may be used as an immunologic marker for acute myeloid leukaemia.