C84.AA
BillableCutaneous T-cell lymphoma, unspecified, in remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C84.AA an HCC code?
Yes. C84.AA 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.AA
For C84.AA 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.AA during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C84.AA is the ICD-10-CM diagnosis code for cutaneous t-cell lymphoma, unspecified, in remission. A type of blood cancer affecting T-cells in the skin that is currently in remission (no active disease). C84.AA 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.AA 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.AA 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.
Only assign this code when documentation explicitly states the patient is in remission or complete response. Because C84.AA 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.AA sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Only assign this code when documentation explicitly states the patient is in remission or complete response
- •This code should not be used if there is any evidence of active disease or recurrence
Clinical Significance
Cutaneous T-cell lymphoma in remission remains a significant diagnosis for risk adjustment because it reflects an ongoing cancer history requiring surveillance. Even in remission, patients need regular dermatologic monitoring, blood work, and imaging to detect recurrence. Accurate coding of remission status distinguishes active disease burden from controlled disease.
Documentation Requirements
- ✓Provider must explicitly state 'in remission' or 'complete response' — absence of treatment alone is insufficient
- ✓Document date remission was achieved and method of confirmation (clinical exam, imaging, biopsy)
- ✓Specify original cutaneous T-cell lymphoma subtype if known (mycosis fungoides, Sezary syndrome, etc.)
- ✓Note ongoing surveillance plan and any maintenance therapy
Commonly Confused Codes
- •C84.A0 (Cutaneous T-cell lymphoma, unspecified site) — Use C84.AA only when remission is documented; C84.A0 is for active disease with unspecified site
- •Z85.79 (Personal history of other malignant neoplasms of lymphoid, hematopoietic tissue) — History codes are used when cancer is completely resolved and no longer under treatment; remission codes indicate cancer still requiring monitoring
- •C84.10 (Sezary disease, unspecified site) — If the specific CTCL subtype is documented, use the subtype-specific code rather than unspecified