C05.0
BillableMalignant neoplasm of hard palate
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C05.0 an HCC code?
Yes. C05.0 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 C05.0
For C05.0to 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 C05.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C05.0 is the ICD-10-CM diagnosis code for malignant neoplasm of hard palate. Cancer that develops in the hard palate, the bony roof of the mouth located at the front portion of the palate. C05.0 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, C05.0 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, C05.0 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.
Hard palate cancers often involve bone invasion; note depth of invasion if documented. Because C05.0 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 C05.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Hard palate cancers often involve bone invasion; note depth of invasion if documented
- •Distinguish from soft palate (C05.1) which is muscular
Clinical Significance
Malignant neoplasm of the hard palate is an uncommon oral cancer arising from the bony roof of the mouth. Hard palate cancers are clinically significant because they frequently involve bone invasion early in their course, and the histological spectrum is broader than other oral sites, including both squamous cell carcinoma and minor salivary gland tumors.
Documentation Requirements
- ✓Biopsy-confirmed histological type (squamous cell carcinoma, adenoid cystic carcinoma, or mucoepidermoid carcinoma are common)
- ✓Specific site documented as hard palate (bony anterior roof of mouth)
- ✓Depth of invasion including bone involvement documented on imaging
- ✓TNM staging and assessment of regional lymph node involvement
- ✓Treatment modality: surgery with possible obturator, radiation, or combined
Commonly Confused Codes
- •C05.1 — Malignant neoplasm of soft palate; the soft palate is the posterior muscular portion vs the anterior bony hard palate
- •C05.8 — Overlapping sites of palate; use when tumor crosses the hard-soft palate junction
- •C05.9 — Palate, unspecified; avoid when hard palate is clearly documented
- •C41.0 — Malignant neoplasm of bones of skull and face; use when tumor originates in palatal bone rather than mucosal surface