Acute myeloid leukemia with giant inclusions: cytochemical and ultrastructural study.

Giant granules formation was investigated in myeloblasts of a patient with acute myelogenous leukemia by means of the combined techniques of peroxidase cytochemistry both in light and electron microscopy. Several pathologic features were noted: first an abnormal packaging of peroxidase in the peripheral area in large azurophilic granulations, second the progressive enlargement of huge vacuolar inclusions resulting from the interaction and fusion of large azurophilic granules with each other, with normal-sized primary granules and with cytoplasmic components. Microcrystalline structure could not be found in giant vacuoles no in vacuolar inclusions resembling Auer bodies. This last finding could explain that no disseminated intravascular coagulation was observed in our patient.