ICD-10 C11.1
Billable / Specific HCC v28: 11Malignant neoplasm of posterior wall of nasopharynx
About ICD-10-CM C11.1
ICD-10-CM code C11.1 represents Malignant neoplasm of posterior wall of nasopharynx. This is a billable/specific code in the Neoplasms chapter (block C11). The 2026 edition of ICD-10-CM C11.1 became effective on October 1, 2025.
Coding Tips for C11.1
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
C11.1 is a CMS-HCC v28 risk-adjustment code (category 11). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under C11.1. Per CMS ICD-10-CM Tabular 2026.
- Malignant neoplasm of adenoid
- Malignant neoplasm of pharyngeal tonsil
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for C11.1
Local Coverage Determinations (LCDs) from CMS MACs that list C11.1 as a covered diagnosis.
Showing top 10 of 926 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing C11.1.
5 Medicare
CPT Codes Commonly Billed with C11.1
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 88358 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 0204U CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 0132U CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 0317U CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 88364 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 88366 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 81433 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 0135U CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 88373 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
- 81436 CMS LCD: Billing and Coding: Genetic Testing for Oncology CMS LCD
Convert C11.1 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| C11.1 | 1471 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To C11.1
Other codes in section C00-C14 (Malignant neoplasms of lip, oral cavity and pharynx).
ICD-10 C11.1, Billing FAQ
Is ICD-10 code C11.1 billable? +
Yes, C11.1 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to C11.1? +
ICD-10 C11.1 includes: Malignant neoplasm of adenoid; Malignant neoplasm of pharyngeal tonsil.
Does C11.1 affect Medicare Advantage HCC risk adjustment? +
Yes. C11.1 maps to CMS-HCC v28 category 11. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with C11.1? +
Procedures frequently paired with C11.1 include: 88358, 0204U, 0132U, 0317U, 88364.
What ICD-9 codes does C11.1 map to? +
Per CMS GEMs, C11.1 maps to ICD-9 codes: 1471. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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