ICD-10 C51.9
Billable / Specific HCC v28: 11Malignant neoplasm of vulva, unspecified
About ICD-10-CM C51.9
ICD-10-CM code C51.9 represents Malignant neoplasm of vulva, unspecified. This is a billable/specific code in the chapter (block C51). The 2026 edition of ICD-10-CM C51.9 became effective on October 1, 2025.
Coding Tips for C51.9
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
C51.9 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 C51.9. Per CMS ICD-10-CM Tabular 2026.
- Malignant neoplasm of external female genitalia NOS
- Malignant neoplasm of pudendum
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 C51.9
Local Coverage Determinations (LCDs) from CMS MACs that list C51.9 as a covered diagnosis.
Showing top 10 of 583 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing C51.9.
1 Cigna
5 Medicare
CPT Codes Commonly Billed with C51.9
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Convert C51.9 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 |
|---|---|---|
| C51.9 | 1844 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To C51.9
Other codes in section C51-C58 (Malignant neoplasms of female genital organs).
ICD-10 C51.9, Billing FAQ
Is ICD-10 code C51.9 billable? +
Yes, C51.9 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 C51.9? +
ICD-10 C51.9 includes: Malignant neoplasm of external female genitalia NOS; Malignant neoplasm of pudendum.
Does C51.9 affect Medicare Advantage HCC risk adjustment? +
Yes. C51.9 maps to CMS-HCC v28 category 11. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What ICD-9 codes does C51.9 map to? +
Per CMS GEMs, C51.9 maps to ICD-9 codes: 1844. 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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