2026 ICD-10-CM Diagnosis Code C04.9Malignant neoplasm of floor of mouth, unspecified
ICD-10-CM Codes›C00–D49›C00-C14›C04
- Billable — Valid for Submission
- Risk Adjusts — HCC 21
- Chronic Condition
C04.9 is a billable ICD-10-CM diagnosis code for malignant neoplasm of floor of mouth, unspecified. 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. Coders also document this condition as carcinoma of floor of mouth. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Head and neck cancers - lip and oral cavity.
For Medicare Advantage risk adjustment, C04.9 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
C04.9 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 floor of mouth
- Malignant melanoma of floor of mouth
- Malignant neoplasm of floor of mouth
- Primary malignant neoplasm of floor of mouth
- Squamous cell carcinoma of floor of mouth
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Patient EducationClinical
Oral Cancer
Oral cancer is cancer of the mouth. It is a type of head and neck cancer. Most oral cancers are squamous cell cancers. They begin in the flat cells that cover the surfaces of your mouth, tongue, and lips. The cancer cells may spread into deeper tissue as the cancer grows.
The full article covers:
- What is oral cancer?
- Who is more likely to develop oral cancer?
- What are the symptoms of oral cancer?
- How is oral cancer diagnosed?
- What are the treatments for oral cancer?
- Can oral cancer be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C04.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C04.9Overview
What is the ICD-10 code for malignant neoplasm of floor of mouth, unspecified?
The ICD-10-CM code for malignant neoplasm of floor of mouth, unspecified is C04.9 (sometimes written as C049). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is C04.9 (Malignant neoplasm of floor of mouth) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of floor of mouth, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C04.9 group to?
When malignant neoplasm of floor of mouth, unspecified 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 C04.9?
Under the General Equivalence Mappings, malignant neoplasm of floor of mouth, unspecified converts to ICD-9-CM 144.9 (mal neo mouth floor NOS). The mapping is a direct match.
What HCC is C04.9?
C04.9 (malignant neoplasm of floor of mouth, unspecified) 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 C04.9 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C04.9 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.
