Age Difference in Immunophenotype of Acute Leukemia

We examined the immunophenotype of 880 cases with acute leukemia and analyzed their age difference in relation to the morphological subtype and the karyotype. We divided the patients into 3 age groups: child (0-15 years), adult (16-59 years) and elderly (60 years and older) group. The diagnoses based on the French-American-British (FAB) criteria and the immunophenotype as follows: 453 patients as acute myeloid leukemia (AML), 366 as precursor B-cell acute lymphoblastic leukemia (ALL) (24 CD10- cases and 342 CD10+ cases), 10 B-cell ALL and 51 T-cell ALL. In AML, there were no significant age differences in the frequency of FAB subtypes. Karyotypically, the frequencies of t(8;21) and 11q23 decreased with age and that of 5/7/8 abnormality increased with age. As for the immunophenotype in each FAB subtype, CD11b in M2 (0%) and CD34 in M3 (0%) were less commonly expressed in the child group than in the other age groups. Whereas Both CD11b (100%) and CD34 (60%) in M4 were more predominantly expressed in the child group than in the other age groups. Lymphoid antigen, CD19 showed a higher frequency (38.5%) in the child M2 than did other age M2 groups, reflecting the distribution pattern of t(8;21) among the 3 age groups. Additionally, the child group more frequently expressed this antigen (33.3%) than the older groups among CD7+ AML. In ALL, the frequency of CD10+ precursor B ALL was more common in the child group (84%) than in the adult group. On the other hand, B-cell ALL showed a lower frequency (0.7%) in the child group and T-cell ALL did a higher frequency (18.3%) in the adult group than any other age groups, respectively. Although the frequency of t(9;22) increased with age in CD10+ precursor-B ALL, myeloid antigen (CD13/CD33) expression evenly distributed among the 3 age groups. Our results suggest that phenotypic heterogeneity gradually emerged with age irrespective of the pattern of karyotype.