NEURAL CELL-ADHESION MOLECULE (CD56)-POSITIVE ACUTE MYELOGENOUS LEUKEMIA AND MYELODYSPLASTIC AND MYELOPROLIFERATIVE SYNDROMES

The CD56 antigen is normally expressed on natural-killer cells but has additionally been shown to be present on a variety of hematologic mal ignancies, including a subset of acute myelogenous leukemia (AML). The re is disagreement, however, about its prognostic significance and its association with specific cytogenetic abnormalities. All clinical sam ples from Tune 1994, through September 1995, with increased myeloblast s were analyzed by multiparameter flow cytometry for anomalous express ion of CD56. patients with CD56(+) blast cells were selected and morph ologic review was performed. Clinical information was obtained, and cy togenetic data were reviewed. Southern blot analysis to detect rearran gement of the mixed lineage leukemia (MLL) gene was performed when pos sible. The samples from 23 of 114 patients studied demonstrated anomal ous expression of CD56 on myeloblasts, including patients with AML, my elodysplastic syndromes (MDS), and chronic myelogenous leukemia in bla st crisis. The samples from 10 of 15 patients with CD56(+) AML demonst rated at least partial monocytic differentiation. Dysplastic features were displayed in the samples of 12 patients. Correlation with specifi c cytogenetic abnormalities was not found. The MLL gene was rearranged in five of 18 patients. Seventeen patients have died, with a median s urvival of 4.6 months for patients with AML. Three have sustained a co mplete remission. One has findings of high-grade myelodysplastic syndr ome. Two were unavailable for follow-up. Expression of CD56 was found in 20% of patients with increased myeloblasts, including patients with high-grade MDS, chronic myelogenous leukemia in blast crisis, and AML . This phenotype was associated with dysplasia, monocytic differentiat ion, and rearrangement of the MLL gene.