Acute childhood leukemia: epidemiologic study by cell type of 1,263 cases at the Children's Cancer Research Foundation in

SUMMARY-The cell-type distribution of 1,263 children with acute leukemia was 43.9 % lymphocytic, 24.6 % undifferentiated, 23.8 % mye-logenous, and 7.8 % monocytic. The lymphocytic excess was limited to a sharp age peak at 2 and 3 years. Myelogenous and undifferentiated categories varied less with age, predominated among males, and had a survival paHern midway between trends for the lymphocytic and mono-cytic types. The differences between lymphocytic and undifferentiated leukemia are surprising, since these cell types share cytochemical charac-teristics and are usually considered as one entity. This study and a review of the literature suggest an excess of certain cell types associated with familial clusters and with genetic diseases predisposing to acute leukemia. In Down's syndrome, however, the increased risk of acute leukemia seems to apply to all cell lines. These and other dissimilarities in the epidemiology of acute leukemia according to cell type signify etiologic heterogeneity and suggest clues to mechanisms which may be involved in blast-cell dif