C05.8
BillableMalignant neoplasm of overlapping sites of palate
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C05.8 an HCC code?
Yes. C05.8 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 C05.8
For C05.8 to 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 C05.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C05.8 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of palate. This code describes cancer that involves multiple overlapping areas of the roof of the mouth (palate). When a tumor spans across different sections of the palate rather than being confined to one specific area, this code is used. C05.8 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, C05.8 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, C05.8 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.
Use this code only when the malignant tumor involves two or more distinct sites of the palate; if the cancer is localized to a single palate site, use a more specific code (C05.0-C05.2). Because C05.8 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 C05.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the malignant tumor involves two or more distinct sites of the palate; if the cancer is localized to a single palate site, use a more specific code (C05.0-C05.2)
- •Ensure documentation clearly indicates the overlapping nature of the neoplasm across palate regions; coordinate with the pathology report to confirm the extent of involvement
Clinical Significance
This overlapping palate cancer code represents tumors crossing anatomical boundaries between the hard palate, soft palate, and uvula. These are often more advanced tumors at diagnosis, requiring complex multidisciplinary treatment approaches and accurate coding to reflect the true extent of disease.
Documentation Requirements
- ✓Pathology and imaging confirming tumor involvement across multiple palate subsites
- ✓Documentation specifying which palate regions are involved (hard palate, soft palate, uvula)
- ✓Evidence that a single primary site cannot be determined from pathology
- ✓Complete TNM staging reflecting overlapping extent
- ✓Surgical planning documentation showing extent of anticipated resection