A 52-year-old man with newly diagnosed chronic myeloid leukemia (CML) in chronic phase undergoes peripheral blood smear examination. All of the following findings are consistent with CML EXCEPT:

Explanation

## Characteristic Features of CML Chronic Phase CML in chronic phase shows a characteristic myeloid proliferation with specific morphologic findings on peripheral blood smear. ## Expected vs. Unexpected Findings | Finding | Typical in CML CP | Mechanism | |---------|-------------------|----------| | **Left shift (myelocytes, metamyelocytes)** | ✓ Yes | Increased granulopoiesis from BCR-ABL1 | | **Basophilia and eosinophilia** | ✓ Yes | Increased basophil and eosinophil precursors | | **Toxic granulations** | ✓ Yes | Immature neutrophils with abnormal granulation | | **Auer rods** | ✗ NO | Characteristic of AML, not CML | ## Key Point: **Auer rods** (Auer bodies) are rod-shaped inclusions composed of fused azurophilic granules. They are pathognomonic for **acute myeloid leukemia (AML)** and myelodysplastic syndrome (MDS), NOT CML. Their presence in a patient with CML would indicate **transformation to blast crisis** (AML-like phase). ## High-Yield: Auer rod = AML or CML blast crisis. In stable CML chronic phase, Auer rods are absent. Their appearance signals leukemic transformation and is a medical emergency. ## Mnemonic: **AUER = AML/Acute Emergency Rods** — when you see Auer rods, think AML or CML in blast crisis, not stable CML. ## Clinical Pearl: The presence of Auer rods in a patient previously diagnosed with CML indicates **accelerated phase or blast crisis** and requires immediate escalation of therapy (consider tyrosine kinase inhibitor intensification or chemotherapy).