Three types of Auer bodies in acute leukemia. Visualization of their protein by negative contrast after peroxidase cytochemistry.

Ten cases of acute granulocytic leukemia with blast cells containing Auer bodies (ABs) have been studied by electron microscopy after cytochemical demonstration of myeloperoxidase. The cytochemical dense reaction product has been used as a dark field to visualize unreactive protein of ABs which may then be easily identified by its negative contrast. This method has allowed us to identify three types of ABs which differ in their substructure. In type I, (five patients with promyelocytic leukemia), our study confirmed that all of the ABs consisted of a hexagonal arrangement of hollow tubes. Cells from four cases of acute myeloblastic leukemia displayed type II ABs, in which a unique pattern of protein associated in a regular linear arrangement with well defined periodicity was identified. Type III appeared characteristic of a subclass of acute myeloblastic leukemia in which large inclusions with Chediak-Higashi-like granules containing numerous micro-ABs were seen. The configuration, size, and organization of the protein in the crystal were distinct from those seen in the two other types of ABs. These features suggest that the nature of the protein in ABs may be heterogeneous.