MINIMALLY DIFFERENTIATED ACUTE MYELOID-LEUKEMIA (AML-MO) - COMPARISONOF 25 CASES WITH OTHER FRENCH-AMERICAN-BRITISH SUBTYPES

We compared the immunophenotypic and karyotypic features of 25 cases o f minimally differentiated acute myeloid leukemia (AML-M0) with those of 247 cases comprising all AML French-American-British (FAB) classifi cation. Myeloperoxidase (MPO) was detectable with a specific monoclona l antibody in all cases of AML-M0, whereas CD13 and CD33 were both neg ative in 4 of the 25 cases. Thus, anti-MPO reliably detects minimal my eloid differentiation in AML-M0. CD34 and terminal deoxynucleotidyl tr ansferase (TdT) were more frequently expressed in AML-MO (96% and 68% of the cases, respectively) than in the other FAB subsets (P < .001 fo r both). By contrast, GP-170 and CD7 were less frequently expressed in AML-M0 than in FAB classes such as M1, M4, and M5 (P = .02 and .003, respectively). A total of 80% of AML-MO cases carried lymphoid markers (including TdT), and 48% showed a coordinate positivity for two or mo re of them. CD2, CD5, CD10, and CD19 were expressed in a similar fashi on among the different FAB groups, whereas CD4 expression was signific antly more frequent in AML-M0, AML-M4, and AML-M5 (P = .014). AML-M0 w as characterized by a more frequent occurrence of complex karyotypes. In addition, approximately 20% of cases had TdT positivity, complex ka ryotypes, and anomalies of chromosome 5 and/or 7, a pattern not observ ed in the other FAB subsets. Finally, 80% of anomalies of chromosome 5 and/or 7 in AML-M0 were comprised within complex karyotypes, whereas only 13% of the remaining FAB cases carried this feature. In summary, AML-M0 frequently expresses immunophenotypic and karyotypic aspects th at are likely to identify a ''stem cell'' pattern. (C) 1997 by The Ame rican Society of Hematology.