What is ICD-10 code C13.1?

C13.1 is the ICD-10-CM diagnosis code for Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect. Cancer of the aryepiglottic fold on the hypopharyngeal side, a tissue fold in the lower throat near the voice box. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C13.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C13.1 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. C13.1 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. C13.1 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 C13.1 map to under V28?

C13.1 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 C13.1 pay in RAF?

C13.1 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 C13.1?

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 C13.1, V28 maps to Lymphoma and Other Cancers at RAF 0.671 while V24 mapped to Colorectal, Bladder, and Other Cancers at RAF 0.307. Both models can still appear in legacy data and in payer-specific lookback periods.

2026 ICD-10-CM C13.1: Malignant neoplasm

C13.1 maps to CMS-HCC V28 21 (RAF 0.671). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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Code lookupC13.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)

C13.1

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

Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect

Cancer of the aryepiglottic fold on the hypopharyngeal side, a tissue fold in the lower throat near the voice box.

Buddy Insight

Malignant neoplasm of the aryepiglottic fold, hypopharyngeal aspect, is a cancer at the boundary between the larynx and hypopharynx.

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

RAF 0.671

CMS-HCC V24

Mapped

HCC 11

Colorectal, Bladder, and Othe...

RAF 0.307

ACA/HHS

Mapped

HCC 11

HHS-HCC 11

Varies by metal level

ESRD/PACE

Mapped

HCC 11

Colorectal, Bladder, and Othe...

RAF 0.059

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

C13Malignant neoplasm of hypopharynx

C13.1Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect

Inclusion Terms

Official

Malignant neoplasm of aryepiglottic fold, marginal zone
Malignant neoplasm of aryepiglottic fold NOS
Malignant neoplasm of interarytenoid fold, marginal zone
Malignant neoplasm of interarytenoid fold NOS

Excludes 2

Official

malignant neoplasm of aryepiglottic fold or interarytenoid fold, laryngeal aspect (C32.1)

Related Child Codes

Official

C13.0Malignant neoplasm of postcricoid region

C13.2Malignant neoplasm of posterior wall of hypopharynx

C13.8Malignant neoplasm of overlapping sites of hypopharynx

C13.9Malignant neoplasm of hypopharynx, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for C13.1 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C13.1 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C13.1 in this effective period.

Use Additional

Official

code to identify:
exposure to environmental tobacco smoke (Z77.22)
exposure to tobacco smoke in the perinatal period (P96.81)
history of tobacco dependence (Z87.891)
occupational exposure to environmental tobacco smoke (Z57.31)

Code Also

Official

ICD-10-CM does not list Code Also instructions for C13.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Pathology-confirmed malignancy

Documentation specifically stating hypopharyngeal aspect of aryepiglottic fold

Clear distinction between hypopharyngeal vs laryngeal surface involvement

Assessment of vocal cord mobility and laryngeal invasion

MEAT Support

HCC Buddy guidance

Pathology-confirmed malignancy

Documentation specifically stating hypopharyngeal aspect of aryepiglottic fold

Clear distinction between hypopharyngeal vs laryngeal surface involvement

Assessment of vocal cord mobility and laryngeal invasion

Audit Caution

HCC Buddy guidance

The most critical pitfall: aryepiglottic fold has both a hypopharyngeal aspect (C13.1) and a laryngeal aspect (C32.1) — the surface determines the code category entirely

Not verifying with endoscopy or imaging reports which surface is primarily involved

Using supraglottic laryngeal code (C32.1) when documentation specifies the hypopharyngeal surface

Failing to document vocal cord mobility which affects staging regardless of which surface is coded

Common Mistakes

HCC Buddy guidance

C32.1 — Supraglottis; the laryngeal aspect of the aryepiglottic fold is coded as supraglottic laryngeal cancer, not C13.1

C10.1 — Anterior surface of epiglottis; an oropharyngeal site distinct from the aryepiglottic fold

C12 — Pyriform sinus; adjacent hypopharyngeal site that may be confused with aryepiglottic fold

C13.8 — Overlapping sites of hypopharynx; use when tumor extends from aryepiglottic fold to other hypopharyngeal sites

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 C13.1 an HCC code?

Yes. C13.1 (Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect) maps to Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, and Other Cancers under V24), with a community non-dual aged RAF of 0.671. It is billable for payment year 2026.

Coder answer: C13.1 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: C13.1
Description: Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect
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 11, Colorectal, Bladder, and Other Cancers

0.307

ESRDHCC 11, Colorectal, Bladder, and Other Cancers

0.059

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 C13.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C13.1

For C13.1 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 C13.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C13.1 is the ICD-10-CM diagnosis code for malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect. Cancer of the aryepiglottic fold on the hypopharyngeal side, a tissue fold in the lower throat near the voice box. C13.1 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of lip, oral cavity and pharynx (c00-c14).

Under the CMS-HCC V28 risk adjustment model, C13.1 maps to Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older CMS-HCC V24 model, C13.1 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.307. 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.

The aryepiglottic fold has both laryngeal and hypopharyngeal aspects; ensure the hypopharyngeal aspect is documented. Because C13.1 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 C13.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•The aryepiglottic fold has both laryngeal and hypopharyngeal aspects; ensure the hypopharyngeal aspect is documented
•This location may affect swallowing and voice function

Clinical Significance

Malignant neoplasm of the aryepiglottic fold, hypopharyngeal aspect, is a cancer at the boundary between the larynx and hypopharynx. The critical coding distinction is that this code captures the hypopharyngeal (outer) surface of the aryepiglottic fold, while the laryngeal (inner) surface is coded as supraglottic laryngeal cancer.

Documentation Requirements

✓Pathology-confirmed malignancy
✓Documentation specifically stating hypopharyngeal aspect of aryepiglottic fold
✓Clear distinction between hypopharyngeal vs laryngeal surface involvement
✓Assessment of vocal cord mobility and laryngeal invasion
✓TNM staging using hypopharyngeal staging criteria

Excludes 2, Not included here, may code separately

malignant neoplasm of aryepiglottic fold or interarytenoid fold, laryngeal aspect (C32.1)

Commonly Confused Codes

•C32.1: Supraglottis; the laryngeal aspect of the aryepiglottic fold is coded as supraglottic laryngeal cancer, not C13.1
•C10.1: Anterior surface of epiglottis; an oropharyngeal site distinct from the aryepiglottic fold
•C12: Pyriform sinus; adjacent hypopharyngeal site that may be confused with aryepiglottic fold
•C13.8: Overlapping sites of hypopharynx; use when tumor extends from aryepiglottic fold to other hypopharyngeal sites