2026 ICD-10-CM Diagnosis Code C31.0Malignant neoplasm of maxillary sinus
ICD-10-CM Codes›C00–D49›C30-C39›C31
- Billable — Valid for Submission
- Risk Adjusts — HCC 21
- Chronic Condition
C31.0 is a billable ICD-10-CM diagnosis code for malignant neoplasm of maxillary 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 - all other types.
For Medicare Advantage risk adjustment, C31.0 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
C31.0 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.
- Adenocarcinoma of accessory sinus
- Adenocarcinoma of maxillary sinus
- Malignant melanoma of accessory sinus
- Malignant melanoma of maxillary sinus
- Malignant neoplasm of maxillary sinus
- Primary adenocarcinoma of accessory sinus
- Primary adenocarcinoma of maxillary sinus
- Primary carcinoma of maxillary sinus
- Primary malignant neoplasm of maxillary sinus
- Primary squamous cell carcinoma of accessory sinus
- Primary squamous cell carcinoma of maxillary sinus
- Squamous cell carcinoma of maxillary sinus
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Malignant neoplasm of antrum (Highmore) (maxillary)
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.
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. |
|---|---|---|---|---|---|---|
| antrum (Highmore) (maxillary) | C31.0 | C78.39 | D02.3 | D14.0 | D38.5 | D49.1 |
| maxilla, maxillary (superior) › antrum | C31.0 | C78.39 | D02.3 | D14.0 | D38.5 | D49.1 |
| maxilla, maxillary (superior) › sinus | C31.0 | C78.39 | D02.3 | D14.0 | D38.5 | D49.1 |
| sinus (accessory) › maxillary | C31.0 | C78.39 | D02.3 | D14.0 | D38.5 | D49.1 |
Patient EducationClinical
Nasal Cancer
Your paranasal sinuses are small hollow spaces around the nose. They are lined with cells that make mucus, which keeps your nose from drying out. The nasal cavity is the passageway just behind your nose. Air passes through it on the way to your throat as you breathe.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C31.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C31.0Overview
What is the ICD-10 code for malignant neoplasm of maxillary sinus?
The ICD-10-CM code for malignant neoplasm of maxillary sinus is C31.0 (sometimes written as C310). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is C31.0 (Malignant neoplasm of accessory sinuses) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of maxillary sinus on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C31.0 group to?
When malignant neoplasm of maxillary 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 C31.0?
Under the General Equivalence Mappings, malignant neoplasm of maxillary sinus converts to ICD-9-CM 160.2 (mal neo maxillary sinus). The mapping is a direct match.
What HCC is C31.0?
C31.0 (malignant neoplasm of maxillary 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. In the Part D prescription drug model it maps to RxHCC 22.
Does C31.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C31.0 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.
