What is ICD-10 code C05.8?

C05.8 is the ICD-10-CM diagnosis code for Malignant neoplasm of overlapping sites of palate. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C05.8 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C05.8 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C05.8 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C05.8 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does C05.8 map to under V28?

C05.8 maps to CMS-HCC V28 HCC 21 (Lymphoma and Other Cancers). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM C05.8: Malignant neoplasm

C05.8 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 Buddy coding tools

ICD-10-CM Code View

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Code lookupC05.8

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)

C05.8

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

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.

Buddy Insight

This overlapping palate cancer code represents tumors crossing anatomical boundaries between the hard palate, soft palate, and uvula.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 011

HHS-HCC 011 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 11

Colorectal/Bladder/and Other ...

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C05Malignant neoplasm of palate C05.8Malignant neoplasm of overlapping sites of palate

Inclusion Terms

Official

No inclusion terms are included in this display for C05.8. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C05.8. Check the code and parent instructions in the Code Book.

Related Codes

Official

C05.0Malignant neoplasm of hard palate C05.1Malignant neoplasm of soft palate C05.2Malignant neoplasm of uvula C05.9Malignant neoplasm of palate, unspecified

Includes

Official

No Includes notes are included in this display for C05.8. 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

Official

No Code First sequencing instructions are included in this display for C05.8. 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

Official

No Code Also instructions are included in this display for C05.8. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Confusing 'overlapping' (tumor spans known multiple sites) with 'unspecified' (site is unknown) — these are fundamentally different concepts

Using this code when the tumor clearly has a single primary palate site with minor extension

Not verifying with pathology that the tumor genuinely crosses anatomical boundaries rather than being a single-site tumor with local spread

Defaulting to this code because two palate sites are mentioned in the note, without confirming the tumor itself spans them

Common Mistakes

HCC Buddy guidance

C05.0 — Hard palate; use when confined to hard palate

C05.1 — Soft palate; use when confined to soft palate

C05.9 — Palate, unspecified; this means the site is unknown, not that it crosses multiple sites

C06.89 — Overlapping sites of other parts of mouth; use when tumor extends beyond palate into other oral structures

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 C05.8 an HCC code?

Yes. C05.8 (Malignant neoplasm of overlapping sites of palate) 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: C05.8 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: C05.8
Description: Malignant neoplasm of overlapping sites of palate
HCC (V28): HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient: 0.671
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers

0.671

ESRDHCC 11, Colorectal/Bladder/and Other Cancers

Not separately weighted

RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors

Not separately weighted

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 C05.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C05.8

For C05.8, 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

C05.8 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 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 C05.8; 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 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). For C05.8, 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 C05.8 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

Commonly Confused Codes

•C05.0: Hard palate; use when confined to hard palate
•C05.1: Soft palate; use when confined to soft palate
•C05.9: Palate, unspecified; this means the site is unknown, not that it crosses multiple sites
•C06.89: Overlapping sites of other parts of mouth; use when tumor extends beyond palate into other oral structures