Morphologic and cytochemical observations on the overt leukemic phase of therapy-related leukemia

Comparison of morphologic and cytochemical features of the leukemic cells of patients with overt acute nonlymphocytic leukemia following therapy for primary malignancies (2 degrees-ANLL) to those of patients with ANLL de novo revealed several differences. No Auer rods were seen in cells of patients with 2 degrees-ANLL, but they were seen in 54 (42%) of 129 cases of ANLL de novo. Only one (4.7%) of 21 patients with 2 degrees-ANLL was classified as M-4 by FAB criteria, compared to 46 (36%) of 129 patients with ANLL de novo classified as M-4. Only one (10%) of 10 patients with 2 degrees-ANLL had more than 10% peroxidase-positive leukemic cells, whereas 19 (95%) of 20 of a control group of patients with ANLL de novo of similar FAB subtypes had more than 10% positive cells. Two of 11 (18%) 2 degrees-ANLL patients had 10% or more naphthol-AS-D chloroacetate esterase-positive cells, in contrast to nine (47%) of 19 patients with ANLL de novo. Nonspecific esterase activity was present in 10% or more of cells in only one (10%) of 10 patients with 2 degrees-ANLL studied, as compared to seven (35%) of 20 of the control group. Previous reports indicate that patients with 2 degrees-ANLL have cytogenetic abnormalities and therapeutic responses that differ from those in ANLL de novo; our findings indicate that there are morphologic and cytochemical differences as well.