2026 ICD-10-CM Diagnosis Code C12Malignant neoplasm of pyriform sinus
ICD-10-CM Codes›C00–D49›C00-C14›C12
- Billable — Valid for Submission
- Risk Adjusts — HCC 21
- Chronic Condition
C12 is a billable ICD-10-CM diagnosis code for malignant neoplasm of pyriform sinus. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 11 through 13, 146 through 148. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Head and neck cancers - hypopharyngeal.
For Medicare Advantage risk adjustment, C12 maps to CMS-HCC Category 21 (Lymphoma and Other Cancers) under the V28 model, adding a risk factor of about 0.671 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C12 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Carcinoma of pyriform fossa
- Malignant neoplasm of pyriform fossa
- Neoplasm of pyriform sinus
- Primary malignant neoplasm of pyriform sinus
- Primary squamous cell carcinoma of hypopharynx
- Primary squamous cell carcinoma of pyriform sinus
- Squamous cell carcinoma of piriform sinus
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Malignant neoplasm of pyriform fossa
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
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| fossa (of) › piriform | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
| fossa (of) › pyriform | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
| hypopharynx, hypopharyngeal NEC › pyriform fossa (sinus) | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
| piriform fossa or sinus | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
| pyriform fossa or sinus | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
| sinus (accessory) › pyriform | C12 | C79.89 | D00.08 | D10.7 | D37.05 | D49.0 |
Patient EducationClinical
Throat Cancer
Throat cancer is a type of head and neck cancer. Throat cancer has different names, depending on which part of the throat is affected. The different parts of your throat are called the oropharynx, the hypopharynx, the nasopharynx, and the larynx, or voice box.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C12 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C12Overview
What is the ICD-10 code for malignant neoplasm of pyriform sinus?
The ICD-10-CM code for malignant neoplasm of pyriform sinus is C12. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is C12 (Malignant neoplasm of pyriform sinus) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of pyriform sinus on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C12 group to?
When malignant neoplasm of pyriform sinus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 11, 12, 13, 146, 147, 148, with relative weights from 0.7971 to 5.4541 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of C12?
Under the General Equivalence Mappings, malignant neoplasm of pyriform sinus converts to ICD-9-CM 148.1 (mal neo pyriform sinus). The mapping is a direct match.
What HCC is C12?
C12 (malignant neoplasm of pyriform sinus) maps to CMS-HCC Category 21 (Lymphoma and Other Cancers), commonly written as HCC 21, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 11 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does C12 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C12 adds a risk adjustment factor of about 0.671 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.493 to 0.739 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, and HCC 20) supersedes it when both are reported. See the full factor table on the HCC 21 category page.
