C94.42
BillableAcute panmyelosis with myelofibrosis, in relapse
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C94.42 an HCC code?
Yes. C94.42 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).
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 C94.42
For C94.42to 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 C94.42 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C94.42 is the ICD-10-CM diagnosis code for acute panmyelosis with myelofibrosis, in relapse. A rare blood cancer where all bone marrow cell lines multiply uncontrollably and simultaneously develop scarring of the bone marrow, and the cancer has returned after a period of remission. C94.42 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, C94.42 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, C94.42 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.
Document that remission was previously achieved before coding relapse. Because C94.42 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 C94.42 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document that remission was previously achieved before coding relapse
- •Distinguish from C94.40 (not in remission) which applies to initial treatment failure
Clinical Significance
Acute panmyelosis with myelofibrosis in relapse signifies recurrence of this rare pan-lineage acute leukemia after prior remission, carrying an extremely poor prognosis. Salvage therapy options are very limited, and relapsed disease often progresses rapidly with accelerating myelofibrosis further complicating treatment.
Documentation Requirements
- ✓Documentation must establish prior remission followed by recurrence, with bone marrow evidence of returning panmyeloid proliferation and worsening fibrosis.
- ✓The interval between remission and relapse, current blast percentage, fibrosis grade, and planned treatment approach should be documented.
Commonly Confused Codes
- •C94.40 (not achieved remission) applies to primary refractory disease.
- •If the relapsed disease shows predominantly one lineage rather than panmyeloid involvement, consider whether a more specific acute leukemia code now applies.
- •D47.1 (primary myelofibrosis) should not be confused with the fibrotic component.