C01 ICD-10-CM Code: Malignant neoplasm of base of tongue
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)
C01
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of base of tongue
Cancer that develops at the base of the tongue, the area where the tongue connects to the throat.
Buddy Insight
Malignant neoplasm of base of tongue is a serious cancer often associated with human papillomavirus (HPV) infection in younger patients and tobacco/alcohol use in older patients.
CMS-HCC V28
MappedHCC 21
RAF 0.545
CMS-HCC V24
MappedHCC 11
RAF 0.306
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 11
RAF 0.0
RXHCC
MappedHCC 22
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Malignant neoplasm of dorsal surface of base of tongue
- Malignant neoplasm of fixed part of tongue NOS
- Malignant neoplasm of posterior third of tongue
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C01 in this effective period.
Related Child Codes
ICD-10-CM does not list child codes under C01 for this display context.
Includes
OfficialICD-10-CM does not list Includes notes for C01 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C01 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C01 in this effective period.
Use Additional
Official- code to identify:
- alcohol abuse and dependence (F10.-)
- history of tobacco dependence (Z87.891)
- tobacco dependence (F17.-)
- tobacco use (Z72.0)
Code Also
OfficialICD-10-CM does not list Code Also instructions for C01 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is C01 an HCC code?
Yes. C01 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, and Other Cancers under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for C01
For C01to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- 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
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C01 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
C01 is the ICD-10-CM diagnosis code for malignant neoplasm of base of tongue. Cancer that develops at the base of the tongue, the area where the tongue connects to the throat. C01 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, C01 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors (HCC 21) with a community, non-dual, aged base RAF weight of 0.545. Under the older CMS-HCC V24 model, C01 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.306. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Base of tongue cancers are often squamous cell carcinomas; verify histology in documentation. Because C01 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for C01 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Base of tongue cancers are often squamous cell carcinomas; verify histology in documentation
- •Ensure this code is not confused with other tongue locations like dorsal or ventral surfaces
Clinical Significance
Malignant neoplasm of base of tongue is a serious cancer often associated with human papillomavirus (HPV) infection in younger patients and tobacco/alcohol use in older patients. Base of tongue cancers are typically diagnosed at advanced stages due to their posterior location and often present with cervical lymph node metastases. Accurate site-specific coding is essential as treatment and prognosis differ by anatomic subsite.
Documentation Requirements
- ✓Pathology report confirming malignancy with histologic type (squamous cell carcinoma most common)
- ✓Documentation specifying base of tongue as the primary tumor site
- ✓TNM staging documented (tumor size, nodal involvement, metastasis)
- ✓HPV/p16 status documented (prognostically significant)
- ✓Treatment plan: surgery, radiation, chemotherapy, or combination
- ✓Active vs historical cancer status clearly documented
Use Additional Code
Commonly Confused Codes
- •C02.4 (Malignant neoplasm of lingual tonsil) - lingual tonsil is distinct lymphoid tissue at the tongue base; verify exact site
- •C02.0 (Malignant neoplasm of dorsal surface of tongue) - dorsal surface is the anterior two-thirds; base is posterior third
- •C09.9 (Malignant neoplasm of tonsil, unspecified) - tonsillar cancer is a separate oropharyngeal site from tongue base
- •Z85.810 (Personal history of malignant neoplasm of tongue) - use for historical cancer that has been treated and is in remission