KIT and mast cell leukemia: KIT is expressed in normal cells and also in solid tumors and hematological malignancies such as gastrointestinal stromal tumor (GIST) [13], small-cell lung cancer [14], colorectal cancer [15], Ewing's tumor [16], chronic myelogenous leukemia (CML) [17], neuroblastoma [18] and mast cell leukemia [19].