This area includes numerous candidate oncogenes such as FLT3, a tyrosine kinase receptor in which activating mutations have been found in acute myeloid leukemia [30], FLT1, a vascular endothelial growth factor receptor found to be expressed in gastric and breast carcinoma cells [31], and FGF9. FGF9 is a potent mitogen that stimulates normal and cancer cell proliferation [32] and appears to be involved in the pathogenesis of a number of tumours such as prostate cancer [33], melanomas [34], brain tumours [35], and breast cancer [36]. This evidence concerns the gene FLT3 and breast cancer.