[Chediak-Higashi-like inclusions in acute myeloblastic leukemia. Ultrastructural study]

The pseudo-Chédiak-Higashi anomaly is characterized by the presence of giant granules in the cytoplasm of blast cells in acute leukemia. We report here a new case of acute myelogenous leukemia (M2 type) with this alteration. The granules were azurophilic or eosinophilic and reacted strongly to peroxidase stain. Ultrastructural studies showed that the granules contained a dense matrix and occasionally "finger print" structures at the periphery; in some inclusions, fibrillar structures of myelinic figures could be seen. The matrix was reactive to peroxidase and small vesicles were prominent in the cytoplasm near the granules. We conclude that the giant granules could have been formed by the fusion of primary granules and/or by the fusion of these small dense vesicles.