C94.30 ICD-10-CM Code: Mast cell leukemia not having achieved remission
C94.30 maps to CMS-HCC V28 20. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C94.30
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMast 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.
Buddy Insight
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.
CMS-HCC V28
MappedHCC 20
Coefficient HCC 20: 1.136 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 009
Code-level coefficient reference
ESRD/PACE
MappedHCC 9
Code-level coefficient reference
RXHCC
MappedHCC 19
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Mast cell leukemia with failed remission
- Mast cell leukemia NOS
Excludes 2
Official- Kaposi's sarcoma of lymph nodes (C46.3)Inherited from C81-C96
- secondary and unspecified neoplasm of lymph nodes (C77.-)Inherited from C81-C96
- secondary neoplasm of bone marrow (C79.52)Inherited from C81-C96
- secondary neoplasm of spleen (C78.89)Inherited from C81-C96
Related Codes
Includes
OfficialNo Includes notes are included in this display for C94.30. Check the code and parent instructions in the Code Book.
Excludes 1
Official- leukemic reticuloendotheliosis (C91.4-)Inherited from C94
- myelodysplastic syndromes (D46.-)Inherited from C94
- personal history of leukemia (Z85.6)Inherited from C94
- plasma cell leukemia (C90.1-)Inherited from C94
Code First
OfficialNo Code First sequencing instructions are included in this display for C94.30. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C94.30. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C94.30. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is C94.30 an HCC code?
Yes. C94.30 (Mast cell leukemia not having achieved remission) maps to HCC 20, Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.136. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C94.30 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C94.30
- Description
- Mast cell leukemia not having achieved remission
- HCC (V28)
- HCC 20 — Lung and Other Severe Cancers
- RAF reference coefficient
- 1.136
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C94.30 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C94.30
For C94.30, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 source-labeled community, non-dual, aged reference coefficient of 1.136. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Mast cell leukemia is distinct from systemic mastocytosis; verify correct diagnosis in documentation. For C94.30, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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.