Auer rods
These are abnormal pink needle shaped polymerized granular structures found in the cytoplasm of abnormal myeloblasts that may be seen in certain myeloid neoplasms. Presence of Auer rods is typically associated with Acute myeloid leukemia (AML) and rarely associated with Refractory Anemia with Excess Blasts II (RAEB-II) which is the most aggressive type of MDS and usually progresses to AML.