C05.9 ICD-10-CM Code: Malignant neoplasm of palate, unspecified
C05.9 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)
C05.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of palate, unspecified
Cancer of the palate when the specific location (hard palate, soft palate, or uvula) is not documented or specified.
Buddy Insight
This unspecified palate cancer code should prompt a documentation improvement effort, as the palate has clearly distinct anatomical regions (hard, soft, uvula) that should be identifiable from clinical examination, imaging, or pathology reports.
CMS-HCC V28
MappedHCC 21
Coefficient HCC 21: 0.671 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 011
Code-level coefficient reference
ESRD/PACE
MappedHCC 11
Code-level coefficient reference
RXHCC
MappedHCC 22
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Malignant neoplasm of roof of mouth
Excludes 2
OfficialNo Excludes 2 notes are included in this display for C05.9. Check the code and parent instructions in the Code Book.
Related Codes
Includes
OfficialNo Includes notes are included in this display for C05.9. Check the code and parent instructions in the Code Book.
Excludes 1
Official- Kaposi's sarcoma of palate (C46.2)Inherited from C05
Code First
OfficialNo Code First sequencing instructions are included in this display for C05.9. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify:Inherited from C05
- alcohol abuse and dependence (F10.-)Inherited from C05
- history of tobacco dependence (Z87.891)Inherited from C05
- tobacco dependence (F17.-)Inherited from C05
- tobacco use (Z72.0)Inherited from C05
Code Also
OfficialNo Code Also instructions are included in this display for C05.9. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is C05.9 an HCC code?
Yes. C05.9 (Malignant neoplasm of palate, unspecified) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C05.9 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C05.9
- Description
- Malignant neoplasm of palate, unspecified
- HCC (V28)
- HCC 21 — Lymphoma and Other Cancers
- RAF reference coefficient
- 0.671
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C05.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C05.9
For C05.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
C05.9 is the ICD-10-CM diagnosis code for malignant neoplasm of palate, unspecified. Cancer of the palate when the specific location (hard palate, soft palate, or uvula) is not documented or specified. C05.9 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, C05.9 maps to Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C05.9; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Use only when specific palate location cannot be determined from documentation. For C05.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C05.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when specific palate location cannot be determined from documentation
- •Query provider for anatomical specificity to assign more precise code
Clinical Significance
This unspecified palate cancer code should prompt a documentation improvement effort, as the palate has clearly distinct anatomical regions (hard, soft, uvula) that should be identifiable from clinical examination, imaging, or pathology reports.
Documentation Requirements
- ✓Pathology confirmation of malignancy in palatal tissue
- ✓Documentation of provider query attempt to specify hard vs soft palate location
- ✓Review of all imaging and surgical reports for location detail
- ✓Staging and treatment information
- ✓Explanation for why specific palate site cannot be determined