Unusual cytoplasmic inclusions in blast cells in acute leukemia.

A 36-year-old man manifested the clinical signs of acute leukemia. Blast cells in the blood and bone marrow contained many large cytoplasmic inclusions. Cytochemical and ultrastructural studies indicated that the leukemic cells were of lymphocytic origin. Three kinds of inclusions were identified on electron microscopy: one type of inclusion contained virus-like particles; another resembled those in cases with hairy cell leukemia; and the third appeared to be autophagic in nature. The presence of the second type of inclusion in the blast cells and the relative chronicity of the clinical course suggest that this patient's disease is of lymphocytic origin, similar to hairy cell leukemia.