HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C91.90
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceLymphoid leukemia, unspecified not having achieved remission
A type of blood cancer affecting lymphoid cells that has not gone into remission or is actively progressing.
Buddy Insight
Lymphoid leukemia, unspecified, not in remission is a nonspecific code used when the exact subtype of lymphoid leukemia cannot be determined but active disease is present.
CMS-HCC V28
MappedHCC 22
RAF 0.0
CMS-HCC V24
MappedHCC 10
RAF 0.675
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 10
RAF 0.0
RXHCC
MappedHCC 19
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Lymphoid leukemia with failed remission
- Lymphoid leukemia NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C91.90 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C91.90 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C91.90 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C91.90 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C91.90 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C91.90 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is C91.90 an HCC code?
Yes. C91.90 maps to Colorectal, Bladder, 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 C91.90
For C91.90to 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 C91.90 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.90 is the ICD-10-CM diagnosis code for lymphoid leukemia, unspecified not having achieved remission. A type of blood cancer affecting lymphoid cells that has not gone into remission or is actively progressing. C91.90 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, C91.90 maps to Colorectal, Bladder, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C91.90 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 when lymphoid leukemia is unspecified and the patient has not achieved remission status. Because C91.90 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 C91.90 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when lymphoid leukemia is unspecified and the patient has not achieved remission status
- •Verify documentation clearly states 'not in remission' or 'active disease' to distinguish from remission codes
Clinical Significance
Lymphoid leukemia, unspecified, not in remission is a nonspecific code used when the exact subtype of lymphoid leukemia cannot be determined but active disease is present. This code should be used sparingly and only when documentation lacks sufficient specificity to assign a more precise code. Unspecified codes may trigger medical record reviews and can indicate incomplete diagnostic workup.
Documentation Requirements
- ✓While this code is used for unspecified lymphoid leukemia, documentation efforts should aim to obtain the specific subtype through immunophenotyping, cytogenetics, and molecular studies.
- ✓The active disease status (not in remission) must be documented.
- ✓Any available diagnostic information, even if incomplete, should be recorded to support potential reclassification to a more specific code.
Commonly Confused Codes
- •More specific codes should always be used when available: C91.10 (B-CLL), C91.00 (ALL, not in remission), C91.30 (B-PLL), C91.40 (HCL), or other specified subtypes.
- •C91.Z0 (other lymphoid leukemia not in remission) is for specified types not classified elsewhere.
- •C95.90 (leukemia, unspecified) is even less specific and should not be used when the lymphoid lineage is confirmed.