CSF1R and neoplasm: It is a potent and selective inhibitor of Class III and Class V split kinase domain receptor tyrosine kinases (RTKs), including VEGFR-1, -2, and -3; PDGFR-α and -β; stem cell factor receptor (KIT); Fms-like tyrosine kinase-3 receptor (FLT3); the RTK encoded by the ret proto-oncogene (RET); and the receptor for M-CSF (CSF-1R) [1-8] each of which have been implicated in tumor cell growth and survival either directly via tumor cell signaling, or, indirectly, via tumor-dependent angiogenesis [9-13].