ICD-10 Code C94.3 – Mast cell leukemia (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C94.3 – Mast cell leukemia
What it is
C94.3 identifies mast cell leukemia, a rare and aggressive mast cell neoplasm. It is used when documentation confirms malignant mast cell proliferation in the blood or bone marrow.
Clinical signs
Clinical features vary; refer to documentation. Common references describe systemic symptoms from mast cell infiltration, such as organ involvement, cytopenias, or circulating abnormal mast cells.
When to use this code
Use C94.3 when the provider diagnoses mast cell leukemia explicitly. It may also apply when pathology or hematology notes document leukemic mast cell disease affecting blood, marrow, or other organs. If the record is unclear, check documentation before coding.
Do not use for
Do not use this code for uncomplicated mastocytosis or other nonleukemic mast cell disorders. If the diagnosis is only suspected, or the record names a different myeloid neoplasm, do not assign C94.3.
Coding tip
Code from the final confirmed diagnosis and verify whether the note distinguishes mast cell leukemia from other mast cell diseases.