Unusual intracytoplasmic inclusions in acute myeloblastic leukemia

Unusual intracytoplasmic inclusions within early granulocyte precursor cells from a patient with acute myeloblastic leukemia (AML) are described. Based upon their staining characteristics and electron- and light-microscopic appearance, the inclusions are distinctly different from any previously described. The inclusions display a variety of shapes, including rectangles, squares, circles, ovals, and irregular, globular forms. Most of the inclusions are refractile and crystal-like. The possible composition of these inclusions is discussed. They are compared with inclusions previously described within leukemic and granulocytic cells.