Acute monocytic leukemias.

Normal monocytes and macrophages are characterized by peculiar ultrastructural and cytochemical features and, in addition, show characteristic membrane properties, a variety of special functional capacities, and important secretory activities. Almost all these cytological features can also be detected in leukemic monocytic cells, and it is quite conceivable that these peculiar features may influence or determine the clinical syndrome associated with the leukemic accumulation of monocytic cells. The morphological identification of monocytic leukemias is a very intriguing diagnostic problem and some controversies still exist concerning their cytological classification. For clinical as well as scientific purposes the diagnosis of monocytic leukemias should rely on the demonstration of specific monocytic features of the leukemic cells. Clinical findings frequently associated with acute monocytic leukemia include increased frequency of leukemic tissue infiltrations as well as increased tendency to hypokalemia and - especially in the "immature" variants - to disorders of hemostasis.