Phenotypic and clinical heterogeneity of CD56-positive acute nonlymphoblastic leukemia.

The precise phenotype and clinical course are described of a subgroup of acute nonlymphoblastic leukemias (ANLL) expressing the NK-cell differentiation antigen CD56. As previously reported, CD56+ leukemias occurred in a frequency of about 20% of ANLL cases showing clinical and immunophenotypical heterogeneity. Carrying various myelomonocytic markers, all cases were diagnosed to be of nonlymphoid origin. Positive or negative expression of CD34 allowed us to distinguish two major subtypes of CD56+ leukemias representing immature and more differentiated cells carrying further differentiation antigens (CD14 and/or CD15) of the myelomonocytic lineages. These phenotypes correlated with the M0, M2, M4, and M5 leukemias of the FAB classification.