Prognostic significance of CD7+CD56+ phenotype and chromosome 5 abnormalities for acute myeloid leukemia M0.

Myeloid/natural killer (NK) cell precursor acute leukemia is an entity of acute leukemia characterized by poor prognosis and a CD7+CD56+ myeloid antigen+ phenotype without light-microscopic myeloperoxidase reactivity. This disease shares several clinical characteristics with acute myeloid leukemia (AML) M0. To clarify the relationship between these 2 leukemias, we analyzed 105 cases of AML M0. Among them, 17 were CD7+ and CD56+, 77 were negative for either antigen, and 11 could not be determined. CD7+CD56+ AML M0 showed onset at significantly lower patient age (median 46 versus 63 years, P = .004). The disease localization and the hematological manifestations were significantly different: CD7+CD56+ AML showed more frequent extramedullary involvement, fewer circulating leukemic blasts, less anemia, and less thrombocytopenia than did AML M0. The cytogenetic aberrations were also unique, because no 5q abnormalities were found in CD7+CD56+ M0. The prognosis of CD7+CD56+ M0 was poor in patients younger than 46 years (P = .03). Multivariate analysis showed that the CD7+CD56+ phenotype was a significant prognostic factor for AML M0, as well as age, circulating blast percentage, and chromosome 5 abnormalities These findings suggest that AML M0 consists of heterogeneous subgroups to be managed separately, and CD7+CD56+ M0 constitutes a distinct subtype of AML M0.