Nonspecific esterase of acute promyelocytic leukemia (M3)

Leukemic cells of 43 patients with acute promyelocytic leukemia (M3) were investigated morphologically and cytochemically to determine the percentage of aberrant enzymes and whether or not the presence impacts on the clinical outcome. Twelve patients (27.9%) showed alpha-naphthyl acetate esterase (ANAE) activity in their leukemic cells, and two of these cases revealed remarkably low myeloperoxidase (MPO) positivity, a pattern seen in monocytic precursors. However, further cytochemical evidence for this monocytic feature, the inhibition of naphthol AS-D acetate esterase (NASDA) activity with sodium fluoride (NASDA-F), was found in only five of these nine patients. In 31 cases (72.1%), there was minimal ANAE activity. Of interest, two of these were devoid of naphthol AS-D chloroacetate esterase (CAE), which is prominently displayed in neutrophilic granulocytes, even though these leukemic cells were 100% intensely positive for MPO activity. Between the two groups with and without ANAE activity, there were no remarkable differences in the distribution of sex and age, hematological findings, and rates of complete response. Our study has confirmed the cytochemical heterogeneity of M3 with no obvious relationship between this heterogeneity and early therapeutic outcome.