CSF1R and systemic mastocytosis: As compared to KIT, whose activating mutations are hallmarks of systemic mastocytosis [5], and gastro-intestinal stromal tumors (GISTs) [6], or to FLT3, whose activating mutations are frequently observed in acute myeloid leukemias (AML) [7], activating mutations in CSF-1R gene have been rarely detected in human tumors [8].