C91.Z2 ICD-10-CM Code: Other lymphoid leukemia, in relapse
C91.Z2 maps to CMS-HCC V28 22 (RAF 0.363). Documentation must support MEAT. MEAT criteria · RAF calculator · free HCC coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C91.Z2
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther lymphoid leukemia, in relapse
This code describes a type of blood cancer called lymphoid leukemia that has returned after a period of remission or improvement. The patient's cancer cells have come back and are actively growing again.
Buddy Insight
Other lymphoid leukemia in relapse indicates recurrence of a specified but uncommon lymphoid leukemia after prior remission.
CMS-HCC V28
MappedHCC 22
RAF 0.363
CMS-HCC V24
MappedHCC 10
RAF 0.675
ACA/HHS
MappedHCC 10
Varies by metal level
ESRD/PACE
MappedHCC 10
RAF 0.111
RXHCC
MappedHCC 19
RAF 1.949
Code Book Path
Inclusion Terms
Official- T-cell large granular lymphocytic leukemia (associated with rheumatoid arthritis)
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C91.Z2 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C91.Z2 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C91.Z2 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C91.Z2 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C91.Z2 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C91.Z2 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 C91.Z2 an HCC code?
Yes. C91.Z2 (Other lymphoid leukemia, in relapse) maps to Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 0.363. It is billable for payment year 2026.
Coder answer: C91.Z2 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C91.Z2
- Description
- Other lymphoid leukemia, in relapse
- HCC (V28)
- HCC 22 — Bladder, Colorectal, and Other Cancers
- RAF
- 0.363
- 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 C91.Z2 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for C91.Z2
For C91.Z2 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.Z2 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
C91.Z2 is the ICD-10-CM diagnosis code for other lymphoid leukemia, in relapse. This code describes a type of blood cancer called lymphoid leukemia that has returned after a period of remission or improvement. The patient's cancer cells have come back and are actively growing again. C91.Z2 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.Z2 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.Z2 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.
Ensure documentation clearly states the leukemia is in 'relapse' or 'recurrence' before assigning this code; remission status must be explicitly documented. Because C91.Z2 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.Z2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly states the leukemia is in 'relapse' or 'recurrence' before assigning this code; remission status must be explicitly documented
- •Verify the specific type of lymphoid leukemia (chronic lymphocytic, acute lymphoblastic, etc.) is documented, as other more specific C91 codes may be more appropriate than the unspecified 'Z2' category
Clinical Significance
Other lymphoid leukemia in relapse indicates recurrence of a specified but uncommon lymphoid leukemia after prior remission. Relapse in rare lymphoid leukemia subtypes poses unique clinical challenges due to limited published treatment data and fewer established salvage protocols. These patients may benefit from referral to specialized centers with experience in rare hematologic malignancies.
Documentation Requirements
- ✓Documentation must confirm the specific subtype, prior remission, and current evidence of disease recurrence.
- ✓Updated diagnostic studies at relapse should be documented, including immunophenotyping and molecular/cytogenetic testing.
- ✓The interval between remission and relapse, prior treatment history, and salvage treatment plan should be recorded.
- ✓Consider clinical trial enrollment and document candidacy assessment.
Commonly Confused Codes
- •C91.Z0 (other lymphoid leukemia not in remission) is for primary refractory disease.
- •C91.Z1 (other lymphoid leukemia in remission) is for controlled disease.
- •C91.92 (lymphoid leukemia, unspecified, in relapse) is for unspecified subtypes.
- •More specific relapse codes should be used when available (C91.12, C91.32, C91.42, etc.).