C94.30
BillableMast cell leukemia not having achieved remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C94.30 an HCC code?
Yes. C94.30 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lung and Other Severe Cancers under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for C94.30
For C94.30 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C94.30 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C94.30 is the ICD-10-CM diagnosis code for mast cell leukemia not having achieved remission. A rare blood cancer where mast cells multiply uncontrollably in the bone marrow and blood, and have not responded to treatment. C94.30 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of lymphoid, hematopoietic and related tissue (c81-c96).
Under the CMS-HCC V28 risk adjustment model, C94.30 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, C94.30 mapped to the same category but with a base RAF weight of 0.973 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Mast cell leukemia is distinct from systemic mastocytosis; verify correct diagnosis in documentation. Because C94.30 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C94.30 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Mast cell leukemia is distinct from systemic mastocytosis; verify correct diagnosis in documentation
- •Use this code only when remission has not been achieved after initial therapy
Clinical Significance
Mast cell leukemia not having achieved remission is an extremely rare and aggressive form of systemic mastocytosis where mast cells constitute at least 20% of bone marrow cells and circulate in the peripheral blood. It carries the worst prognosis among mast cell neoplasms with median survival measured in months.
Documentation Requirements
- ✓Documentation must include bone marrow biopsy demonstrating at least 20% mast cells, peripheral blood smear findings showing circulating mast cells, serum tryptase levels (typically markedly elevated), and KIT D816V mutation status.
- ✓Treatment response confirming no remission achievement must be recorded.