Why Are Auer Rods Formed

Auer rods (see arrow in image) are cytoplasmic inclusions which result from an abnormal fusion of the primary (azurophilic) granules. Single or multiple Auer rods may be seen in the cytoplasm of a cell. If more than one is present, they are frequently close together and may even be overlapping.

Are Auer rods pathognomonic?

Auer rods, first reported by John Auer in 1906 and first recognised by Thomas McCrae, are considered pathognomonic of myeloid differentiation.

Does all AML have Auer rods?

Auer rods are a hallmark of acute myeloid leukemia but occasionally are seen in myelodysplastic syndromes (MDSs) or chronic myelomonocytic leukemia, rarely in cases with fewer than 5% blasts.