Chronic myelomonocytic leukemia: an ultrastructural study by transmission and scanning electron microscopy.

The hematologic findings in three cases of chronic myelomonocytic leukemia are presented, with results of ultrastructural studies by transmission and scanning electron microscopy on two of the cases. In the peripheral blood there was a dual, non-lymphocytic, markedly increased population of granulocytes and monocytes. The granulocytes showed marked nuclear abnormality and nuclear cytoplasmic organelle asynchrony. In the marrow the majority of the cells appeared granulocytic but atypical forms and intermediate difficult to distinguish from monocyte precursors were evident by electron microscopy. The ultrastructural findings lend some support to the concept that the neoplastic granulocytes and monocytes having a common precursor.