Electron microscopic and peroxidase cytochemical analysis of pink pseudo-Chediak-Higashi granules in acute myelogenous leukemia

Giant round pink inclusions (congruent to 2 micrometers) were seen in neutrophilic myeloblasts, promyelocytes, and myelocytes from three patients with acute myelogenous leukemia. On preliminary examination of the bone marrow smears, these inclusions looked like ingested red blood cells in that they were pink and not azurophilic. The bone marrow specimens were processed for the electron microscopic demonstration of peroxidase with 3,3'-diaminobenzidine and H2O2 at pH 7.6. In all three cases, the inclusions were determined to be large peroxidase-positive granules since they were limited by a single unit membrane and, unlike endocytized red blood cells, were not contained within phagocytic vasuoles. The granules were homogeneously dense for peroxidase and showed no obvious crystalline structure when examined stained or unstained on grid. We believe that they correspond to the giant pink round granules Van Slyck and Rebuck observed in immature leukemic granulocytes in 1974 and termed the pseudo-Chediak-Higashi anomaly. Like the giant purple granules seen in leukemia with this anomaly, these granules also appear to be an abnormal variant of peroxidase-positive azurophil (primary) granules. Their lack of azurophilia is due to the absence of sulfated glycoaminoglycans.