C91.91
BillableLymphoid leukemia, unspecified, in remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C91.91 an HCC code?
Yes. C91.91 maps to Bladder, Colorectal, and Other 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 C91.91
For C91.91to 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 C91.91 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.91 is the ICD-10-CM diagnosis code for lymphoid leukemia, unspecified, in remission. A type of blood cancer affecting lymphoid cells that is currently in remission, meaning cancer cells are not detectable. C91.91 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, C91.91 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model, C91.91 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.
Use this code only when documentation explicitly states the patient is in remission. Because C91.91 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 C91.91 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when documentation explicitly states the patient is in remission
- •Remission status must be clearly documented in the medical record to support this code selection
Clinical Significance
Lymphoid leukemia, unspecified, in remission indicates that a lymphoid leukemia of undetermined subtype has responded to treatment. The unspecified nature of this code limits its clinical utility and may indicate incomplete diagnostic documentation. Even in remission, efforts should be made to determine the specific leukemia subtype for accurate prognostication and surveillance planning.
Documentation Requirements
- ✓Documentation must explicitly state remission status.
- ✓Any available subtype information (immunophenotype, cytogenetics, morphology) should be recorded to potentially reclassify to a more specific code.
- ✓The treatment that achieved remission and ongoing surveillance plan should be documented.
- ✓Consider querying the provider for additional diagnostic specificity.
Commonly Confused Codes
- •More specific remission codes are preferred: C91.11 (B-CLL in remission), C91.01 (ALL in remission), C91.41 (HCL in remission).
- •C91.Z1 (other lymphoid leukemia in remission) is for specified types not elsewhere classified.
- •Z85.6 (personal history of leukemia) should not be used in place of this code when active surveillance is ongoing.