What is ICD-10 code C81.91?

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. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C81.91 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C81.91 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C81.91 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C81.91 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does C81.91 map to under V28?

C81.91 maps to CMS-HCC V28 21 (Lymphoma and Other Cancers). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does C81.91 pay in RAF?

C81.91 carries a community, non-dual, aged (CNA) RAF weight of 0.671 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for C81.91?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C81.91, V28 maps to Lymphoma and Other Cancers at RAF 0.671 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

2026 ICD-10-CM C81.91: Hodgkin lymphoma

C81.91 maps to CMS-HCC V28 21 (RAF 0.671). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC81.91Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)

C81.91

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

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.

Buddy Insight

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.

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

RAF 0.671

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 12

HHS-HCC 12

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 21

Hodgkin Lymphoma and Other Ca...

RAF 0.410

Code Book Path

Official

C81Hodgkin lymphoma

C81.9Hodgkin lymphoma, unspecified

C81.91Hodgkin lymphoma, unspecified, lymph nodes of head, face, and neck

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C81.91 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C81.91 in this effective period.

Related Child Codes

Official

C81.90Hodgkin lymphoma, unspecified, unspecified site

C81.92Hodgkin lymphoma, unspecified, intrathoracic lymph nodes

C81.93Hodgkin lymphoma, unspecified, intra-abdominal lymph nodes

C81.94Hodgkin lymphoma, unspecified, lymph nodes of axilla and upper limb

C81.95Hodgkin lymphoma, unspecified, lymph nodes of inguinal region and lower limb

Includes

Official

ICD-10-CM does not list Includes notes for C81.91 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C81.91 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C81.91 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C81.91 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C81.91 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Using unspecified type code when pathology has identified a specific subtype

Not updating the code once pathology results and subtype classification become available

Confusing 'unspecified type' with 'other type' — these have different clinical implications

Coding lymphadenopathy instead of the confirmed lymphoma diagnosis

Common Mistakes

HCC Buddy guidance

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

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C81.91 an HCC code?

Yes. C81.91 (Hodgkin lymphoma, unspecified, lymph nodes of head, face, and neck) maps to Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 0.671. It is billable for payment year 2026.

Coder answer: C81.91 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C81.91
Description: Hodgkin lymphoma, unspecified, lymph nodes of head, face, and neck
HCC (V28): HCC 21 — Lymphoma and Other Cancers
RAF: 0.671
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers

0.671

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 21, Hodgkin Lymphoma and Other Cancers

0.410

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work C81.91 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

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.

Coder workflow notes

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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 Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older V24 model, C81.91 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 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