{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"CD117 is a tyrosine-kinase receptor for stem cell factor (SCF), also known as “steel factor” or “c-kit ligand”. C-kit is a polypeptide that activates bone marrow precursors of a number of blood cells, but its receptor is also present in other cells. C-kit mutations in the interstitial cells of Cajal in the digestive tract are probably the key to Gastrointestinal Stromal Tumors (GISTs), and explain the efficacy of imatinib in the management of these rare malignancies."}]},{"type":"paragraph","children":[{"type":"text","value":"CD117 is found on interstitial cells of Cajal, germ cells, bone marrow stem cells, melanocytes, breast epithelium and mast cells. This receptor is found on a wide variety of tumor cells (Follicular and Papillary Carcinoma of the Thyroid, Adenocarcinomas from endometrium, lung, ovary, pancreas, breast; Malignant Melanoma, Endodermal Sinus Tumor, Small-cell Carcinoma) but has been particularly useful in differentiating Gastrointestinal Stromal Tumors (GIST) from Kaposi’s Sarcoma and tumors of smooth-muscle origin."}]}]}