C12 ICD-10-CM Code: Malignant neoplasm of pyriform sinus
C12 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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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 guidanceMalignant 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
MappedHCC 21
Coefficient HCC 21: 0.671 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 011
Code-level coefficient reference
ESRD/PACE
MappedHCC 11
Code-level coefficient reference
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Malignant neoplasm of pyriform fossa
Excludes 2
OfficialNo Excludes 2 notes are included in this display for C12. Check the code and parent instructions in the Code Book.
Related Codes
No related codes are included in this display for C12. Check the Code Book for the complete code path.
Includes
OfficialNo Includes notes are included in this display for C12. Check the code and parent instructions in the Code Book.
Excludes 1
OfficialNo Excludes 1 notes are included in this display for C12. Check the code and parent instructions in the Code Book.
Code First
OfficialNo Code First sequencing instructions are included in this display for C12. Check the code and parent instructions in the Code Book.
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)
- tobacco dependence (F17.-)
- tobacco use (Z72.0)
Code Also
OfficialNo Code Also instructions are included in this display for C12. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 C12 an HCC code?
Yes. C12 (Malignant neoplasm of pyriform sinus) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C12 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
- C12
- Description
- Malignant neoplasm of pyriform sinus
- HCC (V28)
- HCC 21 — Lymphoma and Other Cancers
- RAF reference coefficient
- 0.671
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C12 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C12
For C12, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
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 source-labeled community, non-dual, aged reference coefficient of 0.671. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
The pyriform sinus is part of the hypopharynx; verify this code is not confused with other hypopharyngeal sites. For C12, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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
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