C84.A2
BillableCutaneous T-cell lymphoma, unspecified, intrathoracic lymph nodes
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C84.A2 an HCC code?
Yes. C84.A2 maps to Lung and Other Severe 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 C84.A2
For C84.A2 to 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 C84.A2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C84.A2 is the ICD-10-CM diagnosis code for cutaneous t-cell lymphoma, unspecified, intrathoracic lymph nodes. A cancer of T cells that primarily affects the skin with involvement of lymph nodes inside the chest cavity. C84.A2 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.A2 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C84.A2 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.
Intrathoracic lymph nodes include mediastinal and hilar nodes; confirm chest involvement is documented. Because C84.A2 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 C84.A2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Intrathoracic lymph nodes include mediastinal and hilar nodes; confirm chest involvement is documented
- •This code indicates systemic spread beyond skin involvement
Clinical Significance
Cutaneous T-cell lymphoma, unspecified, involving intrathoracic lymph nodes indicates cutaneous lymphoma that has progressed to involve mediastinal or hilar nodes. Intrathoracic nodal involvement in a cutaneous T-cell lymphoma suggests significant systemic spread beyond typical skin-confined disease. This represents advanced staging and changes the treatment approach from skin-directed to systemic therapy.
Documentation Requirements
- ✓Original skin biopsy confirming cutaneous T-cell lymphoma
- ✓Chest imaging documenting intrathoracic lymph node involvement
- ✓Node biopsy or PET avidity confirming lymphomatous involvement
- ✓TNMB staging incorporating intrathoracic nodal findings
- ✓Treatment plan reflecting systemic disease