Which cell inclusion is considered pathognomonic for acute myeloid leukemia (AML)?

Auer rods are cytoplasmic inclusions found in myeloid cells and are considered pathognomonic for acute myeloid leukemia (AML). Their presence indicates the differentiation of myeloid precursors and is typically observed in with acute myeloid leukemia, particularly in patients with certain subtypes of the disease. Auer rods can appear as single or multiple rods or can take on a more convoluted appearance. Their formation relates to the abnormal maturation of myeloid cells, a hallmark of AML.

In contrast, smudge cells are associated with chronic lymphocytic leukemia and are indicative of lymphoid malignancies rather than myeloid. Reed Sternberg cells are characteristic of Hodgkin lymphoma and do not relate to AML. Bence Jones protein is associated with multiple myeloma and reflects the presence of free light chains of immunoglobulin in the urine, which is not relevant to acute myeloid leukemia. Hence, Auer rods are the defining inclusion in this context, solidifying their classification as pathognomonic for AML.