C91.Z0
BillableOther lymphoid leukemia 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.Z0 an HCC code?
Yes. C91.Z0 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.Z0
For C91.Z0to 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.Z0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.Z0 is the ICD-10-CM diagnosis code for other lymphoid leukemia not having achieved remission. This code describes a type of blood cancer called lymphoid leukemia that is not in remission, meaning the cancer cells are still present and active in the body. It is used when the leukemia does not fit into other more specific lymphoid leukemia categories. C91.Z0 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.Z0 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.Z0 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, so documentation must confirm active disease. Because C91.Z0 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.Z0 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, so documentation must confirm active disease
- •Ensure you have reviewed the complete leukemia diagnosis to confirm it is 'other lymphoid leukemia' rather than chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia (ALL), or other specified types, as those have their own specific codes
Clinical Significance
Other lymphoid leukemia not in remission represents specified lymphoid leukemia subtypes that do not fit into the more common classifications (CLL, ALL, HCL, PLL, Burkitt, ATLL). This category captures rare entities such as T-cell large granular lymphocytic leukemia, aggressive NK-cell leukemia, and other uncommon lymphoid neoplasms that are actively being treated or have not responded to therapy.
Documentation Requirements
- ✓Documentation should specify the exact subtype of lymphoid leukemia even though ICD-10-CM classifies it under 'other.' Pathology reports with immunophenotyping, cytogenetics, and morphologic description should be documented.
- ✓Active disease status (not in remission) must be explicitly stated, along with treatment history and current disease burden assessment.
Commonly Confused Codes
- •C91.90 (lymphoid leukemia, unspecified) is for truly unspecified cases where the subtype is unknown.
- •Specific codes should be used when available: C91.10 (B-CLL), C91.40 (HCL), C91.30 (B-PLL), etc.
- •C91.A0 (Burkitt leukemia) has its own specific code.
- •C95.90 (leukemia, unspecified) is even less specific and should not be used when lymphoid lineage is confirmed.