What is ICD-10 code C12?

C12 is the ICD-10-CM diagnosis code for Malignant neoplasm of pyriform sinus. Cancer that develops in the pyriform sinus, a small pouch-shaped area on either side of the lower throat. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C12 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C12 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. C12 is a payment HCC under the CMS risk adjustment model. Under the CMS-HCC V28 risk adjustment model it maps to Lymphoma and Other Cancers with a community, non-dual, aged base RAF weight of 0.671. Under the older CMS-HCC V24 model it maps to Colorectal, Bladder, and Other Cancers at RAF 0.307. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. HCC Buddy maintains the V28 and V24 mapping, RAF weight, and MEAT documentation criteria for C12 sourced directly from the CMS-HCC model files.

Yes. C12 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. C12 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.

What is the V28 vs V24 difference for C12?

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 C12, 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.

What should coders know when reporting C12?

The pyriform sinus is part of the hypopharynx; verify this code is not confused with other hypopharyngeal sites Pyriform sinus cancers often present late due to the deep location and may have poor prognosis Because C12 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

C12: Malignant neoplasm of pyriform sinus — ICD-10 | Lymphoma and Other Cancers, Colorectal

ICD-10-CM Code View

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Code lookupC12Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

C12

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

Malignant neoplasm of pyriform sinus

Cancer that develops in the pyriform sinus, a small pouch-shaped area on either side of the lower throat.

Buddy Insight

Malignant neoplasm of the pyriform sinus is the most common hypopharyngeal cancer, accounting for approximately 65-85% of all hypopharyngeal malignancies.

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

C1Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)

C12Malignant neoplasm of pyriform sinus

Inclusion Terms

Official

Malignant neoplasm of pyriform fossa

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C12 in this effective period.

Related Child Codes

Official

ICD-10-CM does not list child codes under C12 for this display context.

Includes

Official

ICD-10-CM does not list Includes notes for C12 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C12 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C12 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 C12 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Pathology-confirmed malignancy (squamous cell carcinoma in vast majority)

Laterality (right or left pyriform sinus)

TNM staging with assessment of laryngeal invasion and cartilage involvement

Assessment of vocal cord mobility as staging criterion

MEAT Support

HCC Buddy guidance

Pathology-confirmed malignancy (squamous cell carcinoma in vast majority)

Laterality (right or left pyriform sinus)

TNM staging with assessment of laryngeal invasion and cartilage involvement

Assessment of vocal cord mobility as staging criterion

Audit Caution

HCC Buddy guidance

Using the general hypopharynx code (C13.9) when pyriform sinus is specifically documented

Not documenting laterality — pyriform sinus cancers are almost always unilateral at presentation

Confusing pyriform sinus cancer with laryngeal cancer (C32.x) when the tumor extends into the larynx

Missing vocal cord mobility assessment which is a critical staging criterion for hypopharyngeal cancers

Common Mistakes

HCC Buddy guidance

C13.0 — Postcricoid region; the postcricoid area is behind the cricoid cartilage, distinct from the pear-shaped pyriform sinus

C13.9 — Hypopharynx, unspecified; avoid when pyriform sinus is documented

C32.1 — Supraglottis; pyriform sinus tumors may extend into the larynx

C13.2 — Posterior wall of hypopharynx; the pyriform sinus is lateral, the posterior wall is midline

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is C12 an HCC code?

Yes. C12 maps to Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, and Other Cancers under V24).

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 C12 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C12

For C12to 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 C12 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C12 is the ICD-10-CM diagnosis code for malignant neoplasm of pyriform sinus. Cancer that develops in the pyriform sinus, a small pouch-shaped area on either side of the lower throat. C12 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, C12 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, C12 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 pyriform sinus is part of the hypopharynx; verify this code is not confused with other hypopharyngeal sites. Because C12 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 C12 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•The pyriform sinus is part of the hypopharynx; verify this code is not confused with other hypopharyngeal sites
•Pyriform sinus cancers often present late due to the deep location and may have poor prognosis

Clinical Significance

Malignant neoplasm of the pyriform sinus is the most common hypopharyngeal cancer, accounting for approximately 65-85% of all hypopharyngeal malignancies. It carries a poor prognosis because tumors in this deep, hidden location often present at advanced stages with regional or distant metastases already present.

Documentation Requirements

✓Pathology-confirmed malignancy (squamous cell carcinoma in vast majority)
✓Laterality (right or left pyriform sinus)
✓TNM staging with assessment of laryngeal invasion and cartilage involvement
✓Assessment of vocal cord mobility as staging criterion
✓Nutritional status evaluation (dysphagia and weight loss are common)

Use Additional Code

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)
tobacco dependence (F17.-)
tobacco use (Z72.0)

Commonly Confused Codes

•C13.0: Postcricoid region; the postcricoid area is behind the cricoid cartilage, distinct from the pear-shaped pyriform sinus
•C13.9: Hypopharynx, unspecified; avoid when pyriform sinus is documented
•C32.1: Supraglottis; pyriform sinus tumors may extend into the larynx
•C13.2: Posterior wall of hypopharynx; the pyriform sinus is lateral, the posterior wall is midline

Code Hierarchy

└C12Malignant neoplasm of pyriform sinus

C12 ICD-10-CM Code: Malignant neoplasm of pyriform sinus

HCC Buddy Code Card

C12

Is C12 an HCC code?

HCC Category Mapping

MEAT Criteria for C12

Get the V28 RAF + MEAT cheat sheet

What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Use Additional Code

Commonly Confused Codes

Code Hierarchy

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