AML-MO: clinical entity or waste basket for immature blastic leukemias? A description of 14 patients. Dutch Slide Review Committee of Leukemias in Adults.

In the period from August 1991 to August 1994, the Dutch Slide Review Committee of Adult Leukemias classified 14 leukemias as AML-M0. We reviewed the clinical characteristics and response to therapy of these patients. Eight patients were male. Patients' age ranged from 7 to 77 years (medium age 62 years). There was a striking homogeneity in morphological appearance of the blasts, being small to medium-sized round cells with often an eccentric nucleus with fine chromatin, several distinct nucleoli, and a high nucleo-cytoplasmic ratio. In addition to myeloid-associated markers such as CD13 and CD33, the blasts of all patients were positive for CD34 and HLA-DR, pointing to their immature differentiation stage. TdT was present in the blasts of 71%, CD7 was positive in the blasts of 42% of the patients. No consistent cytogenetic abnormalities were found. With respect to the treatment outcome, four patients achieved a complete remission after remission-induction treatment. The median survival was 4.5 months. Our present study shows AML-M0 to be an immature leukemia, uniform in morphology and immunological phenotype, with no consistent cytogenetic phenotype and with a poor clinical outcome.