CD117, commonly known as c-kit or stem cell factor receptor, is a “KIT-proto-oncogene receptor tyrosine kinases” expressed in non-malignant cells, including hematopoietic stem cells (HSCs), melanocytes, mast cells, and breast epithelium, but not on plasma cells, gastrointestinal stromal tumors, acute leukemias, myelodysplastic syndromes, monoclonal gammopathies and MM. The gene discussed is KIT; the disease is myelodysplastic syndrome.