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C06.80 ICD-10-CM Code: Malignant neoplasm of overlapping sites of unspecified parts of mouth

C06.80 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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Code lookupC06.80

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

C06.80

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

Malignant neoplasm of overlapping sites of unspecified parts of mouth

Cancer involving multiple overlapping areas of the mouth when the specific parts cannot be identified.

Buddy the Bee presenting code insight

Buddy Insight

This code represents oral cancer spanning multiple overlapping mouth sites where the specific parts involved are unspecified.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 21

Coefficient HCC 21: 0.671 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 011

Code-level coefficient reference

ESRD/PACE

HCC 11

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C06Malignant neoplasm of other and unspecified parts of mouthC06.8Malignant neoplasm of overlapping sites of other and unspecified parts of mouthC06.80Malignant neoplasm of overlapping sites of unspecified parts of mouth

Inclusion Terms

Official

No inclusion terms are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Related Codes

Official
C06.89Malignant neoplasm of overlapping sites of other parts of mouth

Includes

Official

No Includes notes are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify:Inherited from C06
  • alcohol abuse and dependence (F10.-)Inherited from C06
  • history of tobacco dependence (Z87.891)Inherited from C06
  • tobacco dependence (F17.-)Inherited from C06
  • tobacco use (Z72.0)Inherited from C06

Code Also

Official

No Code Also instructions are included in this display for C06.80. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Pathology confirming malignancy involving multiple oral sites
Documentation indicating overlapping involvement across mouth regions
Provider query documentation explaining why specific sites cannot be identified
Imaging reports describing extent of tumor involvement

MEAT Support

HCC Buddy guidance
Pathology confirming malignancy involving multiple oral sites
Documentation indicating overlapping involvement across mouth regions
Provider query documentation explaining why specific sites cannot be identified
Imaging reports describing extent of tumor involvement

Audit Caution

HCC Buddy guidance
Using this code when specific overlapping sites are actually documented (use C06.89 instead)
Confusing overlapping (cancer spans multiple sites) with unspecified (location unknown)
Not reviewing imaging and surgical reports that often contain more specific site information than clinical notes
Failing to attempt a provider query to determine which specific oral structures are involved

Common Mistakes

HCC Buddy guidance
C06.89 — Overlapping sites of other parts of mouth; use when at least one specific site can be identified
C06.9 — Mouth, unspecified; use when there is no overlapping involvement, just unknown location
C14.8 — Overlapping sites of lip, oral cavity and pharynx; use when tumor extends beyond mouth into pharynx
C04.8 — Overlapping sites of floor of mouth; use when overlapping is confined to floor of mouth

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 C06.80 an HCC code?

Yes. C06.80 (Malignant neoplasm of overlapping sites of unspecified parts of mouth) 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: C06.80 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
C06.80
Description
Malignant neoplasm of overlapping sites of unspecified parts of mouth
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 C06.80 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C06.80

For C06.80, 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

C06.80 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of unspecified parts of mouth. Cancer involving multiple overlapping areas of the mouth when the specific parts cannot be identified. C06.80 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, C06.80 maps to Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. 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 documentation indicates overlapping sites but the exact locations are unspecified. For C06.80, 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 C06.80 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 documentation indicates overlapping sites but the exact locations are unspecified
  • •Review pathology reports to determine if more specific site codes are appropriate

Clinical Significance

This code represents oral cancer spanning multiple overlapping mouth sites where the specific parts involved are unspecified. This combination of overlapping nature and lack of specificity suggests documentation gaps that should be addressed through provider queries and imaging review.

Documentation Requirements

  • ✓Pathology confirming malignancy involving multiple oral sites
  • ✓Documentation indicating overlapping involvement across mouth regions
  • ✓Provider query documentation explaining why specific sites cannot be identified
  • ✓Imaging reports describing extent of tumor involvement
  • ✓TNM staging reflecting the advanced, multi-site nature of the disease

Commonly Confused Codes

  • •C06.89: Overlapping sites of other parts of mouth; use when at least one specific site can be identified
  • •C06.9: Mouth, unspecified; use when there is no overlapping involvement, just unknown location
  • •C14.8: Overlapping sites of lip, oral cavity and pharynx; use when tumor extends beyond mouth into pharynx
  • •C04.8: Overlapping sites of floor of mouth; use when overlapping is confined to floor of mouth

Child Codes

C06.80Malignant neoplasm of overlapping sites of unspecified parts of mouth
HCC 21
C06.89Malignant neoplasm of overlapping sites of other parts of mouth
HCC 21

Code Hierarchy

└C06Malignant neoplasm of other and unspecified parts of mouth└C06.8Malignant neoplasm of overlapping sites of other and unspecified parts of mouth└C06.80Malignant neoplasm of overlapping sites of unspecified parts of mouth
└C06.80Malignant neoplasm of overlapping sites of unspecified parts of mouth

Also searched as

  • C06 80
  • C0680

For C06.80, 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.

C06.80 maps to CMS-HCC V28 category 21, Lymphoma and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C06.80. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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