Distinct lymphoblastic and myeloblastic populations in TdT positive acute myeloblastic leukemia: evidence by...

Double-immunofluorescent staining for the enzyme terminal deoxynucleotidyl transferase (TdT) as a marker of primitive lymphoblasts, and for the VIM-D5 antigen as a differentiation antigen of the myeloid system gave direct evidence for distinct lymphoblastic and myeloblastic populations (mixed leukemic cell populations) in seven patients with acute leukemia. The percentage of malignant TdT positive cells contributing to a leukemic cell bulk with unequivocal signs of myeloid origin was between 10 and 80%. A defect at the level of a common progenitor cell giving rise to both the TdT and the VIM-D5 positive blast cell population is discussed.