Auer rod-like inclusions in adult common acute lymphoblastic leukemia.

We report a case of adult common acute lymphoblastic leukemia, defined by enzyme histochemistry and immunophenotypic analysis, which had rod-shaped cytoplasmic inclusions that on Wright's-stained peripheral blood smear resembled Auer rods. Electron microscopic analysis of a buffy coat preparation revealed that the inclusions were not characteristic of Auer rods, but rather that they were composed of concentric lamellar structures with no limiting membrane and were closely associated with the nuclear membrane. Therefore, the presence of Auer rod-like inclusions in blasts on a Wright's-stained peripheral blood smear does not preclude a diagnosis of acute lymphoblastic leukemia.