C91.91 ICD-10-CM Code: Lymphoid leukemia, unspecified, in remission
C91.91 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C91.91
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceLymphoid leukemia, unspecified, in remission
A type of blood cancer affecting lymphoid cells that is currently in remission, meaning cancer cells are not detectable.
Buddy Insight
Lymphoid leukemia, unspecified, in remission indicates that a lymphoid leukemia of undetermined subtype has responded to treatment.
CMS-HCC V28
MappedHCC 22
Coefficient HCC 22: 0.363 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 010
Code-level coefficient reference
ESRD/PACE
MappedHCC 10
Code-level coefficient reference
RXHCC
MappedHCC 19
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C91.91. Check the code and parent instructions in the Code Book.
Excludes 2
Official- Kaposi's sarcoma of lymph nodes (C46.3)Inherited from C81-C96
- secondary and unspecified neoplasm of lymph nodes (C77.-)Inherited from C81-C96
- secondary neoplasm of bone marrow (C79.52)Inherited from C81-C96
- secondary neoplasm of spleen (C78.89)Inherited from C81-C96
Related Codes
Includes
OfficialNo Includes notes are included in this display for C91.91. Check the code and parent instructions in the Code Book.
Excludes 1
Official- personal history of leukemia (Z85.6)Inherited from C91
Code First
OfficialNo Code First sequencing instructions are included in this display for C91.91. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C91.91. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C91.91. Check the code and parent instructions in the Code Book.
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 C91.91 an HCC code?
Yes. C91.91 (Lymphoid leukemia, unspecified, in remission) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C91.91 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
- C91.91
- Description
- Lymphoid leukemia, unspecified, in remission
- HCC (V28)
- HCC 22 — Bladder, Colorectal, and Other Cancers
- RAF reference coefficient
- 0.363
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C91.91 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C91.91
For C91.91, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 source-labeled community, non-dual, aged reference coefficient of 0.363. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Use this code only when documentation explicitly states the patient is in remission. For C91.91, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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.