ICD-10 Code C96.2 – Malignant mast cell neoplasm (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C96.2 – Malignant mast cell neoplasm
What it is
C96.2 identifies a malignant neoplasm of mast cells, a rare cancer arising from cells involved in allergic and inflammatory responses. Use it when the record documents a malignant mast cell tumor or mast cell leukemia.
Clinical signs
Clinical features vary; refer to documentation. Findings may include mast cell proliferation with systemic involvement, organ enlargement, skin lesions, or symptoms related to mediator release, but the chart should support malignancy.
When to use this code
Use C96.2 when the provider clearly documents malignant mast cell neoplasm, mast cell sarcoma, or mast cell leukemia. Apply it for confirmed malignant disease, not for suspected cases or nonspecific mast cell disorders. Check documentation for the exact diagnosis wording.
Do not use for
Do not use this code for benign mastocytosis, cutaneous mastocytosis, or other nonmalignant mast cell conditions. If the record only says “mast cell disorder” without malignancy, check documentation.
Coding tip
Code the malignancy only when the provider states it explicitly; otherwise, query for clarification before assigning C96.2.