Age Difference in Immunophenotype of Acute Leukemia (Report‪)‬

Abstract: 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. Key words: Age difference, immunophenotype, acute leukemia