Extent of lineage involvement of FLT3/ITD. Flow-sorted lymphocytes (L) and myeloblasts (B) from 12 patients positive for FLT3/ITD were tested for the presence of FLT3/ITD mutations; results from 6 patients are displayed. The first 4 patients (patients 10, 17, 22, and 23) had FLT3/ITD involvement of both CD34⁺/CD33^--derived CFU-GM and BFU-E colonies. Patients 18 and 19 had FLT3/ITD involvement of CD34⁺/CD33^- CFU-GM colonies only. M indicates molecular weight marker.