C84.Z0
BillableOther mature T/NK-cell lymphomas, unspecified site
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C84.Z0 an HCC code?
Yes. C84.Z0 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.Z0
For C84.Z0 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.Z0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C84.Z0 is the ICD-10-CM diagnosis code for other mature t/nk-cell lymphomas, unspecified site. A rare type of mature T-cell or NK-cell blood cancer with an unspecified location in the body. C84.Z0 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.Z0 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.Z0 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.
Use this code only when the specific anatomical site of involvement cannot be determined from documentation. Because C84.Z0 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.Z0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the specific anatomical site of involvement cannot be determined from documentation
- •If any site information is available, use a more specific code (Z1-Z7) rather than Z0
Clinical Significance
This code captures rare mature T-cell or natural killer cell lymphomas that do not fit specific ICD-10 categories such as mycosis fungoides, Sezary disease, or anaplastic large cell lymphoma. These include aggressive subtypes like angioimmunoblastic T-cell lymphoma, hepatosplenic T-cell lymphoma, and extranodal NK/T-cell lymphoma. The unspecified site designation should prompt a query for additional anatomical detail.
Documentation Requirements
- ✓Pathology report with immunophenotyping confirming mature T-cell or NK-cell lineage
- ✓Specific T/NK-cell lymphoma subtype when available (angioimmunoblastic, hepatosplenic, enteropathy-associated, etc.)
- ✓Attempt to obtain anatomical site documentation from imaging or clinical notes before using unspecified site
- ✓Current treatment status and staging information
Commonly Confused Codes
- •C84.40 (Peripheral T-cell lymphoma, not elsewhere classified, unspecified site) — Use C84.4x for PTCL-NOS specifically; C84.Z is for other subtypes not listed elsewhere in C84
- •C84.A0 (Cutaneous T-cell lymphoma, unspecified, unspecified site) — C84.A is specifically for cutaneous subtypes; C84.Z covers non-cutaneous mature T/NK-cell lymphomas
- •C86.0-C86.6 (Other specified types of T/NK-cell lymphoma) — Check if the subtype fits a C86 category before defaulting to C84.Z