C94.21 ICD-10-CM Code: Acute megakaryoblastic leukemia, in remission
C94.21 maps to CMS-HCC V28 17 (RAF 4.209). Documentation must support MEAT. 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)
C94.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceAcute megakaryoblastic leukemia, in remission
A rare blood cancer where immature megakaryoblasts multiply uncontrollably, and the cancer has responded well to treatment with no detectable disease.
Buddy Insight
Acute megakaryoblastic leukemia in remission indicates that this rare megakaryocyte-lineage leukemia has responded to treatment.
CMS-HCC V28
MappedHCC 17
RAF 4.209
CMS-HCC V24
MappedHCC 8
RAF 2.659
ACA/HHS
MappedHCC 8
Varies by metal level
ESRD/PACE
MappedHCC 8
RAF 0.353
RXHCC
MappedHCC 19
RAF 1.949
Code Book Path
Inclusion Terms
Official- Acute myeloid leukemia M7
- Acute megakaryocytic leukemia
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C94.21 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C94.21 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C94.21 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C94.21 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C94.21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C94.21 in this effective period.
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 C94.21 an HCC code?
Yes. C94.21 (Acute megakaryoblastic leukemia, in remission) maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic under the CMS-HCC V28 risk adjustment model (and Metastatic Cancer and Acute Leukemia under V24), with a community non-dual aged RAF of 4.209. It is billable for payment year 2026.
Coder answer: C94.21 is billable and maps to V28 HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C94.21
- Description
- Acute megakaryoblastic leukemia, in remission
- HCC (V28)
- HCC 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
- RAF
- 4.209
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so 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 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.
Work C94.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for C94.21
For C94.21 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 C94.21 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
C94.21 is the ICD-10-CM diagnosis code for acute megakaryoblastic leukemia, in remission. A rare blood cancer where immature megakaryoblasts multiply uncontrollably, and the cancer has responded well to treatment with no detectable disease. C94.21 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, C94.21 maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic (HCC 17) with a community, non-dual, aged base RAF weight of 4.209. Under the older CMS-HCC V24 model, C94.21 maps to Metastatic Cancer and Acute Leukemia (HCC 8) with a community, non-dual, aged base RAF weight of 2.659. 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.
Code only when documentation explicitly states remission has been achieved. Because C94.21 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 C94.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Code only when documentation explicitly states remission has been achieved
- •Remission status should be supported by clinical evidence such as bone marrow biopsy or blood count normalization
Clinical Significance
Acute megakaryoblastic leukemia in remission indicates that this rare megakaryocyte-lineage leukemia has responded to treatment. In children with Down syndrome, outcomes are generally more favorable, while adult cases have lower remission rates and higher relapse risk, making surveillance particularly important.
Documentation Requirements
- ✓Remission confirmation requires bone marrow biopsy demonstrating less than 5% blasts with resolution of megakaryoblastic proliferation and improvement of fibrosis.
- ✓Documentation should include the remission date, whether complete or partial, the resolution status of myelofibrosis, and ongoing consolidation or surveillance plan.