ICD-10 Diagnosis Code for Chronic Myeloid Leukemia
The ICD-10 diagnosis code for Chronic Myeloid Leukemia (CML) is C92.1, with the fifth character specifying the disease phase: C92.10 for chronic phase (unspecified remission status), C92.11 for chronic phase in remission, and C92.12 for chronic phase in relapse.
Understanding CML Phase Classification
The diagnosis code must reflect the specific phase of CML, as this directly impacts treatment decisions and prognosis:
Chronic Phase (C92.10-C92.12)
- Chronic phase CML represents 90-95% of newly diagnosed cases and is defined by <15% blasts in peripheral blood and bone marrow according to European LeukemiaNet (ELN) criteria 1, 2
- The WHO classification defines chronic phase slightly differently, requiring <10% blasts 1
- Most patients are diagnosed in chronic phase, often with leukocytosis (frequently >100 × 10⁹/L), thrombocytosis, immature granulocytes, basophilia, and splenomegaly in >50% of cases 1, 2
Accelerated Phase (C92.11-C92.12)
- Accelerated phase is defined by 15-29% blasts in peripheral blood or bone marrow per ELN criteria, which is used in virtually all clinical trials 1, 2
- Additional criteria include >20% basophils, persistent thrombocytosis or thrombocytopenia unrelated to therapy, or clonal chromosomal abnormalities in Philadelphia-positive cells 1
- WHO criteria define accelerated phase as 10-19% blasts, creating a discrepancy that clinicians must navigate 1
Blast Phase/Blast Crisis (C92.20-C92.22)
- Blast phase is defined by ≥30% blasts in peripheral blood or bone marrow, or extramedullary blast involvement according to ELN criteria 1, 2
- WHO criteria use a threshold of ≥20% blasts 1
- This represents transformation to acute leukemia and carries significantly worse prognosis 1
Essential Diagnostic Confirmation Required for Coding
Before assigning any CML diagnosis code, confirmation must include:
- Demonstration of the Philadelphia chromosome t(9;22)(q34;q11) or BCR-ABL1 fusion gene is mandatory for CML diagnosis 1, 2, 3
- Conventional cytogenetics detects the Philadelphia chromosome in 90-95% of cases 4
- In the 5% of cases where the Philadelphia chromosome cannot be detected by standard cytogenetics, FISH or RT-PCR must confirm the BCR-ABL1 fusion 1
- Patients without detectable Philadelphia chromosome or BCR-ABL1 fusion represent atypical CML (a separate disease entity) and should not be coded as C92.1 1
Critical Coding Pitfalls to Avoid
- Do not code CML based solely on peripheral blood findings without molecular or cytogenetic confirmation of BCR-ABL1 positivity 2, 5
- The fifth character must accurately reflect the current disease phase, as this determines treatment intensity and prognosis 1, 2
- When ELN and WHO criteria conflict (particularly for accelerated phase), use ELN criteria as these guide treatment decisions in clinical practice 1
- Ensure the code reflects remission status when applicable, as patients achieving deep molecular response have dramatically different outcomes 6