C51.0 maps to CMS-HCC V28 22. 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

HCC Buddy Code Card

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

Code lookupC51.0

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of female genital organs (C51-C58)

C51.0

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

Malignant neoplasm of labium majus

Cancer that starts in the larger outer folds of the female external genitalia (labia majora).

Buddy Insight

Malignant neoplasm of the labium majus is a vulvar cancer affecting the outer, larger folds of the female external genitalia.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 22

Bladder, Colorectal, and Othe...

Coefficient HCC 22: 0.363 (Community Non-Dual Aged (CNA))

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 012

HHS-HCC 012 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 11

Colorectal/Bladder/and Other ...

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

C51Malignant neoplasm of vulva C51.0Malignant neoplasm of labium majus

Inclusion Terms

Official

Malignant neoplasm of Bartholin's [greater vestibular] gland

Excludes 2

Official

No Excludes 2 notes are included in this display for C51.0. Check the code and parent instructions in the Code Book.

Related Codes

Official

C51.1Malignant neoplasm of labium minus C51.2Malignant neoplasm of clitoris C51.8Malignant neoplasm of overlapping sites of vulva C51.9Malignant neoplasm of vulva, unspecified

Includes

Official

malignant neoplasm of skin of female genital organsInherited from C51-C58

Excludes 1

Official

carcinoma in situ of vulva (D07.1)Inherited from C51

Code First

Official

No Code First sequencing instructions are included in this display for C51.0. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C51.0. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C51.0. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Specific anatomical site confirmed as labium majus (not labium minus or other vulvar structure)

Histological type (squamous cell carcinoma accounts for approximately 90%)

Tumor grade and TNM staging

Depth of invasion (critical for staging vulvar cancer)

MEAT Support

HCC Buddy guidance

Specific anatomical site confirmed as labium majus (not labium minus or other vulvar structure)

Histological type (squamous cell carcinoma accounts for approximately 90%)

Tumor grade and TNM staging

Depth of invasion (critical for staging vulvar cancer)

Audit Caution

HCC Buddy guidance

Confusing labium majus (outer fold) with labium minus (inner fold) — review anatomical documentation carefully

Using the unspecified vulva code when the specific structure is identified in pathology

Not capturing depth of invasion which is critical for FIGO staging of vulvar cancer

Failing to code concurrent in situ disease when both invasive and preinvasive components are documented

Common Mistakes

HCC Buddy guidance

C51.1 — Malignant neoplasm of labium minus; different anatomical structure — labium majus is the outer fold, labium minus is the inner fold

C51.9 — Malignant neoplasm of vulva, unspecified; use only when the specific vulvar structure is not documented

C51.8 — Overlapping sites of vulva; use when tumor spans multiple vulvar structures

D07.1 — Carcinoma in situ of vulva; preinvasive disease, not yet malignant invasion

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 C51.0 an HCC code?

Yes. C51.0 (Malignant neoplasm of labium majus) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. 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: C51.0 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C51.0
Description: Malignant neoplasm of labium majus
HCC (V28): HCC 22 — Bladder, Colorectal, and Other Cancers
RAF reference coefficient: 0.363
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers

0.363

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 C51.0 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C51.0

For C51.0, 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

C51.0 is the ICD-10-CM diagnosis code for malignant neoplasm of labium majus. Cancer that starts in the larger outer folds of the female external genitalia (labia majora). C51.0 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of female genital organs (c51-c58).

Under the CMS-HCC V28 risk adjustment model, C51.0 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a source-labeled community, non-dual, aged reference coefficient of 0.363. 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.

Verify histology type (squamous cell carcinoma is most common) for additional specificity. For C51.0, 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 C51.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify histology type (squamous cell carcinoma is most common) for additional specificity
•Confirm laterality if documented (left, right, or bilateral) as this may affect staging

Clinical Significance

Malignant neoplasm of the labium majus is a vulvar cancer affecting the outer, larger folds of the female external genitalia. Vulvar cancer is relatively uncommon, accounting for approximately 5% of gynecological malignancies. It is strongly associated with Human Papillomavirus infection and chronic vulvar dermatoses such as lichen sclerosus.

Documentation Requirements

✓Specific anatomical site confirmed as labium majus (not labium minus or other vulvar structure)
✓Histological type (squamous cell carcinoma accounts for approximately 90%)
✓Tumor grade and TNM staging
✓Depth of invasion (critical for staging vulvar cancer)
✓Lymph node assessment — inguinofemoral node status
✓Human Papillomavirus status if documented
✓Laterality (right, left, or bilateral) when documented

Commonly Confused Codes

•C51.1: Malignant neoplasm of labium minus; different anatomical structure: labium majus is the outer fold, labium minus is the inner fold
•C51.9: Malignant neoplasm of vulva, unspecified; use only when the specific vulvar structure is not documented
•C51.8: Overlapping sites of vulva; use when tumor spans multiple vulvar structures
•D07.1: Carcinoma in situ of vulva; preinvasive disease, not yet malignant invasion