C84.Z4 ICD-10-CM Code: Other mature T/NK-cell lymphomas, lymph nodes of axilla and upper limb
C84.Z4 maps to CMS-HCC V28 20. 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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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C84.Z4
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther mature T/NK-cell lymphomas, lymph nodes of axilla and upper limb
A rare type of mature T-cell or NK-cell blood cancer affecting lymph nodes in the armpits and upper arms.
Buddy Insight
Other mature T/NK-cell lymphoma involving lymph nodes of axilla and upper limb represents a rare aggressive neoplasm requiring specific anatomical documentation.
CMS-HCC V28
MappedHCC 20
Coefficient HCC 20: 1.136 (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 21
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C84.Z4. 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 C84.Z4. Check the code and parent instructions in the Code Book.
Excludes 1
Official- personal history of non-Hodgkin lymphoma (Z85.72)Inherited from C84, C84.Z
- angioimmunoblastic T-cell lymphoma (C86.50)Inherited from C84, C84.Z
- blastic NK-cell lymphoma (C86.40)Inherited from C84, C84.Z
- enteropathy-type T-cell lymphoma (C86.20)Inherited from C84, C84.Z
- extranodal NK-cell lymphoma, nasal type (C86.00)Inherited from C84, C84.Z
- hepatosplenic T-cell lymphoma (C86.10)Inherited from C84, C84.Z
- primary cutaneous CD30-positive T-cell proliferations (C86.60)Inherited from C84, C84.Z
- subcutaneous panniculitis-like T-cell lymphoma (C86.30)Inherited from C84, C84.Z
- T-cell leukemia (C91.1-)Inherited from C84, C84.Z
Code First
OfficialNo Code First sequencing instructions are included in this display for C84.Z4. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C84.Z4. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C84.Z4. 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 C84.Z4 an HCC code?
Yes. C84.Z4 (Other mature T/NK-cell lymphomas, lymph nodes of axilla and upper limb) maps to HCC 20, Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.136. 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: C84.Z4 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C84.Z4
- Description
- Other mature T/NK-cell lymphomas, lymph nodes of axilla and upper limb
- HCC (V28)
- HCC 20 — Lung and Other Severe Cancers
- RAF reference coefficient
- 1.136
- 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 C84.Z4 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C84.Z4
For C84.Z4, 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
C84.Z4 is the ICD-10-CM diagnosis code for other mature t/nk-cell lymphomas, lymph nodes of axilla and upper limb. A rare type of mature T-cell or NK-cell blood cancer affecting lymph nodes in the armpits and upper arms. C84.Z4 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, C84.Z4 maps to Lung and Other Severe Cancers (HCC 20) with a source-labeled community, non-dual, aged reference coefficient of 1.136. 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.
Ensure documentation specifies axillary or upper limb lymph node involvement. For C84.Z4, 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 C84.Z4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation specifies axillary or upper limb lymph node involvement
- •Verify this is not a secondary site of spread from a primary tumor elsewhere
Clinical Significance
Other mature T/NK-cell lymphoma involving lymph nodes of axilla and upper limb represents a rare aggressive neoplasm requiring specific anatomical documentation. Accurate site coding to axillary or epitrochlear lymph node regions of the upper extremity supports treatment planning and staging assessment. These lymphomas have variable prognosis depending on subtype, with some being highly aggressive and treatment-resistant.
Documentation Requirements
- ✓Pathology confirmation of mature T-cell or NK-cell lineage via immunophenotyping (CD3+, CD4/CD8, CD56 for NK-cell)
- ✓Imaging or clinical documentation confirming involvement of lymph nodes of axilla and upper limb
- ✓Specific subtype identification when possible (angioimmunoblastic, hepatosplenic, extranodal NK/T-cell, etc.)
- ✓Ann Arbor staging and whether B-symptoms (fever, night sweats, weight loss) are present
Commonly Confused Codes
- •C84.A series (Cutaneous T-cell lymphoma): C84.Z is for non-cutaneous mature T/NK-cell subtypes; verify the lymphoma is NOT a cutaneous subtype
- •C84.4x (Peripheral T-cell lymphoma, not elsewhere classified): C84.4 is specifically for PTCL-NOS; C84.Z covers other named subtypes not classified elsewhere
- •C86.x (Other specified T/NK-cell lymphomas): Check C86 codes first for hepatosplenic (C86.1), enteropathy-associated (C86.2), or subcutaneous panniculitis-like (C86.3) subtypes