Auer rod Information and Courses from MediaLab, Inc.

Blast cells may be seen in the spinal fluid when cell proliferation in acute leukemia or lymphoma spreads to the central nervous system. The arrows indicate the two blasts in this field. Notice the smooth chromatin pattern in the nucleus and prominent nucleoli in both cells. Notice that an Auer rod is present in the cytoplasm in the blast to the right. The Auer rod indicates that these blasts are myeloblasts rather than lymphoblasts. A segmented neutrophil and several red cells can also be seen.

An Auer rod is indicated by the arrow in this blast cell.

Auer rods are red staining, needle-like bodies seen in the cytoplasm of myeloblasts, and/or progranulocytes in leukemia. Auer rods 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. Their identification is very important because, if found, they can confirm the presence of myeloblasts indicating the presence of a myeloid (non-lymphoblastic) leukemia. They can also be seen in myeloid blast crisis in chronic granulocytic leukemia. Auer rods are never seen in lymphoblasts. This differentiation is important because the treatment of lymphoblastic and myeloblastic leukemia are different. Auer Rods are always classified as pathological.

One Auer rod can be seen in the cytoplasm of this cell at approximately 11 o'clock. Auer rods are easily missed. When many blasts are present on a slide, you should look for them carefully.

Illustrated in the photograph is a immature granulocyte with a distinct rod-shaped intracytoplasmic inclusion. This inclusion is known as an Auer rod, which is seen in up to 10% of blast cells in patients with acute myelogenous leukemia. An Auer red is the fusion of primary granules into rod-like inclusions.