However, abnormal ligand-dependent signaling occurring in the absence of mutations and reflecting altered expression of KIT and/or Kitl/KITLG contributes to the pathogenesis of not only non-neoplastic disorders such as gastrointestinal dysmotilities and allergies [1,21,22] but also various cancers including subsets of GIST, acute myeloid leukemia, small-cell lung carcinoma, breast and colorectal cancer, ovarian cancer and neuroblastoma [1,9,11-13]. The gene discussed is KIT; the disease is neoplastic disease or syndrome.