Auer rod

Auer rods (or Auer bodies) are large, crystalline cytoplasmic inclusion bodies sometimes observed in myeloid blast cells during acute myeloid leukemia, acute promyelocytic leukemia, high-grade myelodysplastic syndromes and myeloproliferative disorders.

Composed of fused lysosomes and rich in lysosomal enzymes, Auer rods are azurophilic and can resemble needles, commas, diamonds, rectangles, corkscrews, or (rarely) granules.

[1] Although Auer rods are named for American physiologist John Auer,[2] they were first described in 1905 by Canadian physician Thomas McCrae, then at Johns Hopkins Hospital,[3] as Auer himself acknowledged in his 1906 paper.

Both McCrae and Auer mistakenly thought that the cells containing the rods were lymphoblasts.

[4]