Which type of leukemia is characterized by the presence of azurophilic granular needles known as Auer rods?

The presence of Auer rods is a key histological feature that is specifically associated with acute myelogenous leukemia (AML). Auer rods are crystalline structures formed by the aggregation of myeloperoxidase-containing granules in myeloid cells and are indicative of myeloid differentiation.

In the context of leukemia, this feature is primarily seen in acute myelogenous leukemia, which arises from myeloid progenitor cells and can present with various clinical symptoms such as fatigue, infections, and bleeding due to bone marrow infiltration. The identification of Auer rods during a bone marrow biopsy or peripheral blood smear is an important diagnostic criterion for AML and helps differentiate it from other types of leukemias.

Other types of leukemia do not typically present with Auer rods. For instance, acute lymphoblastic leukemia involves lymphoid progenitors, and thus, does not show these myeloid markers. Chronic lymphocytic leukemia primarily affects mature B cells and is associated with different morphological findings, typically featuring small, mature lymphocytes. Chronic myelogenous leukemia is a myeloproliferative disorder that is characterized by the Philadelphia chromosome and increased granulocyte proliferation but does not prominently feature Auer rods in the classic sense.

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