C84.40
BillablePeripheral T-cell lymphoma, not elsewhere classified, unspecified site
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C84.40 an HCC code?
Yes. C84.40 maps to Lymphoma and Other 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 C84.40
For C84.40 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 C84.40 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C84.40 is the ICD-10-CM diagnosis code for peripheral t-cell lymphoma, not elsewhere classified, unspecified site. A type of T-cell lymphoma (a blood cancer) that does not fit into other specific categories and affects an unspecified location in the body. C84.40 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, C84.40 maps to Lymphoma and Other Cancers (HCC 19) with a community, non-dual, aged base RAF weight of 0.105. Under the older V24 model, C84.40 mapped to the same category but with a base RAF weight of 0.675 — V28 recalibrated weights across the entire model. 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 site of involvement is not documented or is unknown. Because C84.40 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 C84.40 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Peripheral T-cell lymphoma, not elsewhere classified, at an unspecified site is an aggressive non-Hodgkin lymphoma originating from mature T-cells that does not fit into other specific T-cell lymphoma categories. This is a heterogeneous group of lymphomas with generally poor prognosis and limited treatment options compared to B-cell lymphomas. Accurate identification is important because peripheral T-cell lymphomas require different treatment protocols than B-cell lymphomas.
Documentation Requirements
- ✓Pathology confirming peripheral T-cell lymphoma with immunohistochemistry demonstrating T-cell markers
- ✓Exclusion of other specific T-cell lymphoma subtypes (mycosis fungoides, Sezary disease, anaplastic large cell lymphoma, etc.)
- ✓Staging documentation including imaging (CT or PET/CT)
- ✓Documentation of specific site if available — query provider if site not specified
- ✓Treatment plan — typically anthracycline-based chemotherapy
Commonly Confused Codes
- •C84.00 — Mycosis fungoides: A cutaneous T-cell lymphoma with distinct biology and treatment; peripheral T-cell lymphoma is a nodal/systemic disease
- •C84.10 — Sezary disease: A leukemic cutaneous T-cell lymphoma, distinct from peripheral T-cell lymphoma
- •C86.0-C86.6 — Other specified T-cell lymphomas: Specific entities like hepatosplenic T-cell lymphoma, subcutaneous panniculitis-like T-cell lymphoma have their own codes
- •C85.10 — Unspecified B-cell lymphoma: Verify T-cell vs. B-cell lineage on immunohistochemistry; treatment is fundamentally different