Morphologic immunophenotypic and cytogenetic patterns of adult acute myeloid leukemia in Saudi Arabia

During a 6-year period we received bone marrow (BM) and peripheral blood (PB) samples from 178 patients with acute myeloid leukemia (AML). All patient BM, and occasionally, PB samples were characterized according to FAB criteria, and by immunophenotyping (IP) and cytogenetics (CG). This report summarizes the findings in the 125 patients who were older than 15 years. Their mean and median ages were 39.4 and 37.0 years. There were 8 (6.4%) M1, 27 (21.6%) M2, 15 (12.0%) M3, 49 (39.2%) M4, 14 (11.2%) M5A, 9 (7.2%) M5B and 2 (1.6%) M6. IP showed that HLA-DR was most strongly and frequently expressed by M1 blasts (53.5%, 86%) and least strongly and frequently expressed by M3 blasts (4.5%, 0%). HLA-DR was also relatively strongly expressed by M4, M5A, M5B (21.5%, 43%; 34.9%, 69%; and 19.2%, 56%, respectively). CD11b was uniformly weakly expressed by all FAB subgroups. CD13 was most strongly and frequently expressed by M4 (20%, 43%), and was relatively weakly and infrequently expressed by the other FAB subtypes (9.5%, 9.2%, 16.4%, 8.4%, 16.3%). CD14 was moderately expressed by M4 (15.2%, 25%) and M5B (14.0%, 22%) and M1 (7.0%, 40%). CD33 was most strongly expressed by M3 blasts (26.3% and 61%), and was most weakly expressed by M5B (10.6% and 22%). Fourteen (11.2%) patients had blasts that showed lymphoid antigens (5 T, 5 B, 5 CALLA) in addition to myeloid characteristics. Fifty-four (51.9%) of 104 patients tested had one or more karyotypic abnormalities, the most frequent of which was 8+. Only the t(15:17) was specific, and was seen in M3. Four patients with anomalous IP had trisomy 21, one of whom also had 11q-. We conclude that Saudi Arabian AML shows FAB patterns similar to patients in the West, and that M3 patients have a characteristic IP and cytogenetic pattern. Apart from this the MIC classification failed to reveal characteristic modes.