KIT and systemic mastocytosis: Ficoll-isolated native bone marrow mononuclear cells from 10 patients with pathologically (CD25/CD117) confirmed bone marrow infiltration (5-40%) were used in a dose-effect viability assay as described before [23]: A technical difficulty occurs with the typically small proportion of mast cells in bone marrow aspirates deriving from patients with diagnosed systemic mastocytosis.