Myeloblastic Auer Rods
Background Information of Myeloblastic Auer Rods
Auer rods are clumps of azurophilic lysosomal granular material that form elongated needles seen in the cytoplasm of leukemic blasts. They can be seen in the leukemic blasts of acute myeloid leukemia with maturation and acute promyelocytic leukemia (known as acute myeloid leukemia M2 and M3, in the FAB classification, respectively) and in high grade myelodysplastic syndromes and myeloproliferative syndromes. They are composed of fused lysosomes/primary neutrophilic granules and contain peroxidase,lysosomal enzymes, and large crystalline inclusions. Morphologically, the Auer "rods" come in all sizes and shapes. They have been typically described as needle-shapes with pointed ends (most common), but may appear in comma-shapes and diamond-shapes; others were long and rectangula more appropriately referred as Auer bodies.
They are also used to distinguish the pre-leukemia myelodysplastic syndromes: refractory anemia with excess blasts 2 (which has Auer rods) from RAEB 1 (which does not), it is noteworthy, though, that rare cases of RAEB1 show rare auer rods, and when they do, they have a worse prognosis.