2027 ICD-10-CM Diagnosis Code C01Malignant neoplasm of base of tongue
ICD-10-CM Codes›C00–D49›C00-C14›C01
- Billable — Valid for Submission
- Risk Adjusts — HCC 21
- Chronic Condition
C01 is a billable ICD-10-CM diagnosis code for malignant neoplasm of base of tongue. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 11 through 13, 146 through 148. Coders also document this condition as carcinoma of base of tongue. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Head and neck cancers - lip and oral cavity.
For Medicare Advantage risk adjustment, C01 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 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C01 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 2027.
Source: CMS Payment Year 2027 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 base of tongue
- Carcinoma of tongue base - dorsal surface
- Malignant neoplasm of base of tongue
- Malignant neoplasm of base of tongue dorsal surface
- Primary carcinoma of base of tongue
- Primary carcinoma of tongue base - dorsal surface
- Primary malignant neoplasm of base of tongue
- Primary malignant neoplasm of dorsal surface of tongue
- Primary squamous cell carcinoma of base of tongue
- Primary tongue carcinoma
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C01: its own notes plus those printed at Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Malignant neoplasm of dorsal surface of base of tongue
- Malignant neoplasm of fixed part of tongue NOS
- Malignant neoplasm of posterior third of tongue
Use Additional Code
Add a second code, after this one, to fully describe the condition.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C01, its category, or a range that includes it.
Applicable To 3
These notes mention C01.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Malignant Posterior Tongue Neoplasm
a primary or metastatic malignant neoplasm that affects the base of the tongue.
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. |
|---|---|---|---|---|---|---|
| tongue › base (dorsal surface) | C01 | C79.89 | D00.07 | D10.1 | D37.02 | D49.0 |
| tongue › fixed part NEC | C01 | C79.89 | D00.07 | D10.1 | D37.02 | D49.0 |
| tongue › posterior (third) | C01 | C79.89 | D00.07 | D10.1 | D37.02 | D49.0 |
| tongue › root | C01 | C79.89 | D00.07 | D10.1 | D37.02 | D49.0 |
| tongue › surface (dorsal) › base | C01 | C79.89 | D00.07 | D10.1 | D37.02 | D49.0 |
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 C01 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C01Overview
What is the ICD-10 code for malignant neoplasm of base of tongue?
The ICD-10-CM code for malignant neoplasm of base of tongue is C01. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C01 (Malignant neoplasm of base of tongue) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of base of tongue on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C01 group to?
When malignant neoplasm of base of tongue is the principal diagnosis on an inpatient stay, it groups to MS-DRG 12, 11, 146, 13, 147, 148, with relative weights from 0.8005 to 5.6129 depending on complications. Higher weights mean higher Medicare reimbursement.
Does C01 need an additional code?
When the condition applies, yes. The Use Additional Code note reads: code to identify: alcohol abuse and dependence (F10.-); history of tobacco dependence (Z87.891); tobacco dependence (F17.-); tobacco use (Z72.0). The additional code is reported after C01.
What is the ICD-9 equivalent of C01?
Under the General Equivalence Mappings, malignant neoplasm of base of tongue converts to ICD-9-CM 141.0 (mal neo tongue base). The mapping is a direct match.
What HCC is C01?
C01 (malignant neoplasm of base of tongue) 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 2027. 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 C01 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C01 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.
