Auer rods in the acute myeloid leukemias: Frequency and methods of demonstration

One hundred and twenty‐five cases of acute myeloid leukemia (AML) were reviewed for the presence of Auer rods by two peroxidase methods. The percentage of Auer rods recognized by Wright‐Giemsa (WG) staining was 20·8% but three times higher by peroxidase staining techniques using either benzidine base as a substrate (PO method) or 3,3′‐diaminobenzidine as a substrate (DAB method). Both PO and DAB methods were equally sensitive in identifying Auer rods, the higher percentage being in FAB types M2 and M4 and lower in M1, M3, and MSB, with none in MSA. Cell counts of at least 100 cells were as accurate as counting cells up to a total of 1000 consecutive blasts.