C81.91
BillableHodgkin lymphoma, unspecified, lymph nodes of head, face, and neck
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C81.91 an HCC code?
Yes. C81.91 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors 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 C81.91
For C81.91 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 C81.91 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C81.91 is the ICD-10-CM diagnosis code for hodgkin lymphoma, unspecified, lymph nodes of head, face, and neck. Hodgkin lymphoma of unspecified type affecting lymph nodes in the head, face, and neck region. C81.91 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, C81.91 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors (HCC 21) with a community, non-dual, aged base RAF weight of 0.545. Under the older CMS-HCC V24 model, C81.91 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.
Confirm documentation specifies head, face, or neck lymph node involvement. Because C81.91 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 C81.91 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm documentation specifies head, face, or neck lymph node involvement
- •This code is appropriate when the Hodgkin subtype is unknown but the anatomical site is clear
Clinical Significance
Hodgkin lymphoma of unspecified type involving head, face, and neck lymph nodes captures a confirmed Hodgkin diagnosis with a documented anatomic site but without histologic subtype information. This commonly occurs when the initial diagnosis is made by an outside provider and detailed pathology is not available. Head and neck lymph nodes are the most common presentation site for Hodgkin lymphoma, accounting for the majority of initial diagnoses.
Documentation Requirements
- ✓Confirmed diagnosis of Hodgkin lymphoma affecting head/face/neck lymph nodes
- ✓Documentation indicating why the histologic subtype is not specified
- ✓Physical exam or imaging confirming head, face, or neck lymph node involvement
- ✓Plan to obtain pathology review for subtype classification when possible
- ✓Encounter-specific assessment and management
Commonly Confused Codes
- •C81.71 — Other Hodgkin lymphoma, head/face/neck: 'other' indicates pathology reviewed but variant does not fit standard categories; 'unspecified' indicates subtype not yet determined
- •C81.11 — Nodular sclerosis Hodgkin lymphoma, head/face/neck: the most common subtype at this site; use when confirmed by pathology
- •C85.11 — Non-Hodgkin B-cell lymphoma, head/face/neck: ensure the lymphoma is confirmed as Hodgkin type