C88.21 ICD-10-CM Code: Heavy chain disease, in remission
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)
C88.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceHeavy chain disease, in remission
A rare blood cancer characterized by abnormal production of incomplete immunoglobulin heavy chains that has responded well to treatment with no active disease.
Buddy Insight
Heavy chain disease in remission indicates this rare lymphoproliferative disorder has responded to treatment.
CMS-HCC V28
MappedHCC 21
RAF 0.545
CMS-HCC V24
MappedHCC 10
RAF 0.675
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 10
RAF 0.0
RXHCC
MappedHCC 21
RAF 0.0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
Official- Franklin disease
- Gamma heavy chain disease
- Mu heavy chain disease
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C88.21 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C88.21 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C88.21 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C88.21 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C88.21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C88.21 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 C88.21 an HCC code?
Yes. C88.21 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors 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 C88.21
For C88.21to 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 C88.21 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
C88.21 is the ICD-10-CM diagnosis code for heavy chain disease, in remission. A rare blood cancer characterized by abnormal production of incomplete immunoglobulin heavy chains that has responded well to treatment with no active disease. C88.21 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, C88.21 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors (HCC 21) with a community, non-dual, aged base RAF weight of 0.545. Under the older CMS-HCC V24 model, C88.21 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.
Confirm remission status through laboratory studies and clinical assessment before assigning this code. Because C88.21 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 C88.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm remission status through laboratory studies and clinical assessment before assigning this code
- •Document the specific heavy chain type and treatment modality used to achieve remission
Clinical Significance
Heavy chain disease in remission indicates this rare lymphoproliferative disorder has responded to treatment. Given the extreme rarity of this condition, remission data is limited, but it generally reflects reduction or disappearance of the abnormal heavy chain protein and improvement in associated symptoms. Ongoing surveillance with serial immunofixation electrophoresis is required to monitor for relapse.
Documentation Requirements
- ✓Provider must explicitly document remission with laboratory evidence showing reduction or absence of the monoclonal heavy chain on immunofixation electrophoresis.
- ✓The original diagnosis confirmation, specific heavy chain type, treatment used, and surveillance plan must be in the record.