What are the aggregates of MPO called in histology?

The aggregates of myeloperoxidase (MPO) are referred to as Auer rods in histological examinations. Auer rods are formed from the fusion of azurophilic granules and are typically found in immature myeloid cells, particularly in acute myeloid leukemia (AML). Their presence is significant and used diagnostically, as they indicate abnormal myeloid differentiation.

MPO is an enzyme present in the granules of myeloid cells, and its aggregates can be visualized as these distinct rod-like structures under the microscope. Their identification plays a critical role in the classification and diagnosis of hematological malignancies. Auer rods are specifically associated with myeloid lineage cells, making them a hallmark of myeloid leukemias, which supports their relevance in clinical practice.