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C88.21 ICD-10-CM Code: Heavy chain disease, in remission

C88.21 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupC88.21

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 guidance

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.

Buddy the Bee presenting code insight

Buddy Insight

Heavy chain disease in remission indicates this rare lymphoproliferative disorder has responded to treatment.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 21

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 010

Code-level coefficient reference

ESRD/PACE

HCC 10

Code-level coefficient reference

RXHCC

HCC 21

Code-level coefficient reference

Code Book Path

Official
C88Malignant immunoproliferative diseases and certain other B-cell lymphomasC88.2Heavy chain diseaseC88.21Heavy chain disease, in remission

Inclusion Terms

Official
  • Franklin diseaseInherited from C88.2
  • Gamma heavy chain diseaseInherited from C88.2
  • Mu heavy chain diseaseInherited from C88.2

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

Official
C88.20Heavy chain disease not having achieved remission

Includes

Official

No Includes notes are included in this display for C88.21. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • B-cell lymphoma, unspecified (C85.1-)Inherited from C88
  • personal history of other malignant neoplasms of lymphoid, hematopoietic and related tissues (Z85.79)Inherited from C88

Code First

Official

No Code First sequencing instructions are included in this display for C88.21. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C88.21. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C88.21. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
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.

MEAT Support

HCC Buddy guidance
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.

Audit Caution

HCC Buddy guidance
Do not assign remission without explicit documentation and supporting laboratory evidence.
Continue using this active malignancy code during surveillance rather than a history code.
Ensure the remission determination is based on specialized immunofixation studies, not routine protein electrophoresis alone.

Common Mistakes

HCC Buddy guidance
C88.20 (heavy chain disease not in remission) indicates active disease.
Z85.79 (personal history of malignant neoplasm of lymphoid tissue) is only for definitively cured disease.
C88.01 (Waldenstrom macroglobulinemia in remission) is a different immunoproliferative disorder.

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 C88.21 an HCC code?

Yes. C88.21 (Heavy chain disease, in remission) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. 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: C88.21 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C88.21
Description
Heavy chain disease, in remission
HCC (V28)
HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient
0.671
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers
0.671
ESRDHCC 10, Lymphoma and Other Cancers
Not separately weighted
RxHCCHCC 21, Lymphomas and Other Hematologic Cancers
Not separately weighted

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 C88.21 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C88.21

For C88.21, 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

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 Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C88.21; use the applicable model and payment year when reviewing the V28 mapping. 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.

Confirm remission status through laboratory studies and clinical assessment before assigning this code. For C88.21, 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 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.

Commonly Confused Codes

  • •C88.20 (heavy chain disease not in remission) indicates active disease.
  • •Z85.79 (personal history of malignant neoplasm of lymphoid tissue) is only for definitively cured disease.
  • •C88.01 (Waldenstrom macroglobulinemia in remission) is a different immunoproliferative disorder.

Child Codes

C88.20Heavy chain disease not having achieved remission
HCC 21
C88.21Heavy chain disease, in remission
HCC 21

Code Hierarchy

└C88Malignant immunoproliferative diseases and certain other B-cell lymphomas└C88.2Heavy chain disease└C88.21Heavy chain disease, in remission
└C88.21Heavy chain disease, in remission

C88.21 code history

Code setChange
FY2025 (effective Oct 1, 2024)Added to the code set

Source: official CMS ICD-10-CM order and addenda files, FY2016 through FY2027.

For C88.21, 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.

C88.21 maps to CMS-HCC V28 category 21, Lymphoma and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C88.21. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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