C06.9
BillableMalignant neoplasm of mouth, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C06.9 an HCC code?
Yes. C06.9 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 C06.9
For C06.9to 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 C06.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C06.9 is the ICD-10-CM diagnosis code for malignant neoplasm of mouth, unspecified. This code represents cancer that has developed in the mouth or oral cavity, but the specific location within the mouth has not been documented or identified. It is used when a patient has been diagnosed with mouth cancer but more detailed information about the exact site is unavailable. C06.9 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, C06.9 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, C06.9 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.
Query the provider for more specific anatomical location (tongue, palate, gums, lip, etc.) as this will allow assignment of a more specific C06.0-C06.8 code and improve clinical documentation. Because C06.9 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 C06.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Query the provider for more specific anatomical location (tongue, palate, gums, lip, etc.) as this will allow assignment of a more specific C06.0-C06.8 code and improve clinical documentation
- •Ensure this code is not used when the cancer site is documented elsewhere (such as lip cancer which has its own C00 category) - verify the documentation carefully to assign the most specific code available
Clinical Significance
Malignant neoplasm of mouth, unspecified, is the least specific oral cavity cancer code and should be considered a last resort. Its use signals that documentation is insufficient to identify even the general area within the oral cavity, representing the greatest documentation improvement opportunity in this code range.
Documentation Requirements
- ✓Pathology confirmation of malignancy within the oral cavity
- ✓Exhaustive review of all available records (imaging, pathology, operative reports) documented
- ✓Provider query attempted and documented for more specific location
- ✓Documentation of why no more specific site can be determined
- ✓Current treatment status and staging
Commonly Confused Codes
- •C06.0 — Cheek mucosa; query provider if any cheek involvement is noted
- •C06.1 — Vestibule of mouth; check if vestibule is mentioned anywhere in records
- •C14.0 — Pharynx, unspecified; ensure the cancer is in the oral cavity, not the pharynx
- •C05.9 — Palate, unspecified; more specific than C06.9 if at least palate is identified