C91.A0
BillableMature B-cell leukemia Burkitt-type not having achieved remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C91.A0 an HCC code?
Yes. C91.A0 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other 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 C91.A0
For C91.A0 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 C91.A0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.A0 is the ICD-10-CM diagnosis code for mature b-cell leukemia burkitt-type not having achieved remission. This is a type of aggressive blood cancer called Burkitt leukemia that starts from immature B cells in the bone marrow and has not gone into remission (improvement). The cancer cells are actively present and the patient is undergoing or needs treatment. C91.A0 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, C91.A0 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C91.A0 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. 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.
Verify the remission status in the medical record - this code specifically indicates the patient has NOT achieved remission, which is critical for accurate coding. Because C91.A0 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 C91.A0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the remission status in the medical record - this code specifically indicates the patient has NOT achieved remission, which is critical for accurate coding
- •Do not use this code if the patient has achieved remission or complete response to treatment; instead use the appropriate remission code (C91.A1)
Clinical Significance
Mature B-cell leukemia Burkitt-type (also known as Burkitt leukemia or L3 ALL) is an extremely aggressive hematologic malignancy characterized by rapidly proliferating mature B cells with a high mitotic index. This leukemia is closely related to Burkitt lymphoma and often presents with high tumor burden, tumor lysis syndrome risk, and central nervous system involvement. The 'not in remission' status indicates active, highly proliferative disease requiring urgent intensive chemotherapy.
Documentation Requirements
- ✓Documentation must confirm the Burkitt-type morphology with characteristic cytogenetics, specifically t(8
- ✓14)(q24
- ✓q32) involving the MYC gene, or variant translocations t(2
- ✓8) or t(8
- ✓22). Ki-67 proliferation index approaching 100% and starry-sky pattern on biopsy should be noted. Active disease status and tumor lysis syndrome risk stratification must be documented. Central nervous system evaluation results should be included.
Commonly Confused Codes
- •C83.70-C83.79 (Burkitt lymphoma) is used when disease predominantly involves lymph nodes and extranodal sites rather than bone marrow/blood.
- •C91.00 (acute lymphoblastic leukemia, not in remission) may be confused but lacks the specific Burkitt-type morphology and MYC translocation.
- •C91.90 (lymphoid leukemia, unspecified) is far less specific.
- •C91.Z0 (other lymphoid leukemia not in remission) should not be used when Burkitt-type is confirmed.