C84.45
BillablePeripheral T-cell lymphoma, not elsewhere classified, lymph nodes of inguinal region and lower limb
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C84.45 an HCC code?
Yes. C84.45 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 C84.45
For C84.45 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 C84.45 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C84.45 is the ICD-10-CM diagnosis code for peripheral t-cell lymphoma, not elsewhere classified, lymph nodes of inguinal region and lower limb. A type of T-cell lymphoma affecting the lymph nodes in the groin and lower legs. C84.45 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, C84.45 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, C84.45 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.
Confirm documentation specifies inguinal region or lower limb lymph node involvement. Because C84.45 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 C84.45 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm documentation specifies inguinal region or lower limb lymph node involvement
- •This includes lymph nodes of the hip, thigh, and lower extremity
Clinical Significance
Peripheral T-cell lymphoma not elsewhere classified involving inguinal and lower limb lymph nodes is an aggressive lymphoma affecting the groin and lower extremity nodal basins. This presentation may be associated with skin involvement on the lower extremities and must be carefully distinguished from cutaneous T-cell lymphoma subtypes. Site-specific coding reflects the distinct clinical presentation and potential complications.
Documentation Requirements
- ✓Pathology confirming PTCL-NOS with appropriate immunohistochemistry
- ✓Imaging or physical examination documenting inguinal and/or lower limb lymph node involvement
- ✓Documentation excluding other specific T-cell lymphoma subtypes
- ✓Clinical staging with notation of disease extent
- ✓Active disease status documented
Commonly Confused Codes
- •C84.65 — Anaplastic large cell lymphoma, ALK-positive, inguinal/lower limb: Requires ALK positivity on pathology, a distinct entity with different prognosis
- •C84.75 — Anaplastic large cell lymphoma, ALK-negative, inguinal/lower limb: Separate morphologic entity from PTCL-NOS
- •C84.A5 — Cutaneous T-cell lymphoma, unspecified, inguinal/lower limb: Cutaneous T-cell lymphoma is a skin-primary disease (mycosis fungoides, Sezary syndrome) distinct from nodal PTCL-NOS
- •C84.48 — PTCL-NOS, multiple sites: Use only when disease is confined to inguinal/lower limb region