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C09.9 ICD-10-CM Code: Malignant neoplasm of tonsil, unspecified

C09.9 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 · free HCC coding tools

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC09.9

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

C09.9

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

Malignant neoplasm of tonsil, unspecified

Cancer of the tonsil where the specific location within the tonsil tissue is not documented or specified in the medical record.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of tonsil, unspecified, is used when tonsillar cancer is diagnosed but the specific subsite within the tonsil is not documented.

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

N/A

—

Not mapped

Code Book Path

Official
C09Malignant neoplasm of tonsilC09.9Malignant neoplasm of tonsil, unspecified

Inclusion Terms

Official
  • Malignant neoplasm of tonsil NOS
  • Malignant neoplasm of faucial tonsils
  • Malignant neoplasm of palatine tonsils

Excludes 2

Official
  • malignant neoplasm of lingual tonsil (C02.4)Inherited from C09
  • malignant neoplasm of pharyngeal tonsil (C11.1)Inherited from C09

Related Codes

Official
C09.0Malignant neoplasm of tonsillar fossaC09.1Malignant neoplasm of tonsillar pillar (anterior) (posterior)C09.8Malignant neoplasm of overlapping sites of tonsil

Includes

Official

No Includes notes are included in this display for C09.9. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C09.9. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C09.9. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify:Inherited from C09
  • alcohol abuse and dependence (F10.-)Inherited from C09
  • exposure to environmental tobacco smoke (Z77.22)Inherited from C09
  • exposure to tobacco smoke in the perinatal period (P96.81)Inherited from C09
  • history of tobacco dependence (Z87.891)Inherited from C09
  • occupational exposure to environmental tobacco smoke (Z57.31)Inherited from C09
  • tobacco dependence (F17.-)Inherited from C09
  • tobacco use (Z72.0)Inherited from C09

Code Also

Official

No Code Also instructions are included in this display for C09.9. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Pathology confirmation of tonsillar malignancy
Provider query documentation for specific tonsillar subsite
HPV/p16 status (essential for oropharyngeal cancer staging)
Laterality

MEAT Support

HCC Buddy guidance
Pathology confirmation of tonsillar malignancy
Provider query documentation for specific tonsillar subsite
HPV/p16 status (essential for oropharyngeal cancer staging)
Laterality

Audit Caution

HCC Buddy guidance
Defaulting to this code without reviewing operative reports or pathology which typically specify fossa vs pillar
Not recognizing that 'tonsillar cancer' in a progress note may have more specific documentation in specialist reports
Confusing palatine tonsils (coded here) with lingual tonsil (base of tongue) or pharyngeal tonsil (adenoid)
Failing to capture HPV status which is critical for tonsillar cancers

Common Mistakes

HCC Buddy guidance
C09.0 — Tonsillar fossa; the most common specific tonsillar subsite — query provider
C09.1 — Tonsillar pillar; check if documentation mentions anterior or posterior pillar
C10.9 — Oropharynx, unspecified; even less specific — at least C09.9 identifies the tonsil
C11.1 — Nasopharyngeal wall; do not confuse pharyngeal tonsil (adenoid) with palatine tonsil

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 C09.9 an HCC code?

Yes. C09.9 (Malignant neoplasm of tonsil, 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: C09.9 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
C09.9
Description
Malignant neoplasm of tonsil, unspecified
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

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 C09.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C09.9

For C09.9, 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

C09.9 is the ICD-10-CM diagnosis code for malignant neoplasm of tonsil, unspecified. Cancer of the tonsil where the specific location within the tonsil tissue is not documented or specified in the medical record. C09.9 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, C09.9 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 C09.9; 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.

This is a default code used when tonsil cancer is diagnosed but the exact anatomical site is not specified in documentation. For C09.9, 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 C09.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •This is a default code used when tonsil cancer is diagnosed but the exact anatomical site is not specified in documentation
  • •Query the provider if possible to obtain more specific site information (C09.0 for palatine tonsil, C09.1 for lingual tonsil, etc.) for more accurate coding

Clinical Significance

Malignant neoplasm of tonsil, unspecified, is used when tonsillar cancer is diagnosed but the specific subsite within the tonsil is not documented. Given the increasing importance of HPV status and precise staging in tonsillar cancer management, coders should make every effort to obtain more specific site documentation.

Documentation Requirements

  • ✓Pathology confirmation of tonsillar malignancy
  • ✓Provider query documentation for specific tonsillar subsite
  • ✓HPV/p16 status (essential for oropharyngeal cancer staging)
  • ✓Laterality
  • ✓Review of operative and imaging reports for subsite detail

Commonly Confused Codes

  • •C09.0: Tonsillar fossa; the most common specific tonsillar subsite: query provider
  • •C09.1: Tonsillar pillar; check if documentation mentions anterior or posterior pillar
  • •C10.9: Oropharynx, unspecified; even less specific: at least C09.9 identifies the tonsil
  • •C11.1: Nasopharyngeal wall; do not confuse pharyngeal tonsil (adenoid) with palatine tonsil

Child Codes

C09.0Malignant neoplasm of tonsillar fossa
HCC 21
C09.1Malignant neoplasm of tonsillar pillar (anterior) (posterior)
HCC 21
C09.8Malignant neoplasm of overlapping sites of tonsil
HCC 21
C09.9Malignant neoplasm of tonsil, unspecified
HCC 21

Code Hierarchy

└C09Malignant neoplasm of tonsil└C09.9Malignant neoplasm of tonsil, unspecified
└C09.9Malignant neoplasm of tonsil, unspecified

Also searched as

  • C09 9
  • C099

For C09.9, 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.

C09.9 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 C09.9. 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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