A 52-year-old man with newly diagnosed chronic myeloid leukemia (CML) in chronic phase undergoes peripheral blood smear examination. The smear shows left shift with myelocytes, metamyelocytes, and bands present. Which of the following is NOT expected on the peripheral blood smear in CML chronic phase?

Explanation

## Peripheral Blood Smear in CML Chronic Phase ### Definition and Characteristics **Key Point:** CML chronic phase is defined by: - <5% blasts in peripheral blood - <5% blasts in bone marrow - <30% basophils + eosinophils combined - Presence of Philadelphia chromosome (BCR-ABL1) ### Expected Findings in Chronic Phase | Finding | Mechanism | Presence in Chronic Phase | |---------|-----------|---------------------------| | **Left shift (myelocytes, metamyelocytes, bands)** | Uncontrolled myeloid proliferation | Yes, hallmark | | **Basophilia** | Increased basophil count; part of myeloid expansion | Yes, common | | **Eosinophilia** | Increased eosinophil count; part of myeloid expansion | Yes, common | | **Blasts <5%** | Controlled proliferation in chronic phase | Yes, by definition | | **Toxic granulations** | Cytoplasmic abnormalities; may be present | Yes, possible | | **Döhle bodies** | Cytoplasmic inclusions of ribosomes; may be present | Yes, possible | | **Blasts >30%** | Indicates acceleration or blast crisis | **NO — this defines accelerated phase/blast crisis** | ### Why >30% Blasts is NOT Chronic Phase **High-Yield:** Blast crisis (or accelerated phase with >30% blasts) represents **progression** from chronic phase and is defined by: - ≥30% blasts in blood or marrow (blast crisis) - 20–29% blasts = accelerated phase - These are separate phases with worse prognosis **Clinical Pearl:** The presence of >30% blasts **disqualifies the diagnosis of chronic phase** — it indicates the patient has progressed to blast crisis, which requires escalation of therapy (e.g., tyrosine kinase inhibitor intensification or stem cell transplant). **Mnemonic:** **CML Phases by Blast %** - **Chronic:** <5% blasts - **Accelerated:** 5–29% blasts (or other criteria) - **Blast Crisis:** ≥30% blasts ### Toxic Changes in CML **Key Point:** Toxic granulations and Döhle bodies reflect cytoplasmic stress and are **not specific to CML** but can occur in severe infections, sepsis, and myeloproliferative disorders.