Mast cell leukemia, in relapse

This code represents mast cell leukemia that has recurred or progressed after a period of remission or successful treatment. It signifies a systemic mast cell disease characterized by the presence of ≥20% mast cells in the bone marrow and signs of organ damage, now in an active phase following a previous period of improvement.

Apply this code when documentation explicitly states a diagnosis of mast cell leukemia and indicates that the disease is currently in relapse. This typically follows a period where the patient was considered to be in remission or had stable disease after initial therapy. Supporting documentation would include physician notes detailing the recurrence of symptoms, elevated mast cell counts, and bone marrow biopsy results confirming active disease.

• Ensure documentation clearly specifies "in relapse" for mast cell leukemia; do not assume relapse without explicit physician statement.
• Distinguish from mast cell leukemia in remission (C94.31) or not specified as in remission or relapse (C94.30).
• Code any associated organ damage or complications of the mast cell leukemia as secondary diagnoses.