Acute basophilic leukemia. A clinical, morphologic, and cytogenetic study of eight cases.

The authors describe eight cases of acute basophilic leukemia. In six of the eight cases, basophilic involvement was not apparent by light microscopic examination. The cases were identified on the basis of ultrastructural evidence for basophil/mast cell differentiation of the blasts with little or no differentiation into other lineages. Ultrastructural analysis revealed immature basophil granules in blasts in all eight cases and theta granules in blasts in four cases. In three cases, ultrastructural evidence of mast cell differentiation also was present, with rare cells showing evidence for both basophil and mast cell differentiation. No clinical features distinguished this group of patients from others with acute myeloid leukemia. Cytogenetically, the cases were heterogeneous. Three had a Philadelphia chromosome; none had a t(6;9). The authors conclude that ultrastructural analysis usually must be used to diagnose acute basophilic leukemia, that acute basophilic leukemia is associated frequently with the Philadelphia chromosome, and that the ultrastructural findings provide evidence for a common origin of basophils and mast cells.