2027 ICD-10-CM Diagnosis Code C51.9Malignant neoplasm of vulva, unspecified
ICD-10-CM Codes›C00–D49›C51-C58›C51
- Billable — Valid for Submission
- Risk Adjusts — HCC 22
- Chronic Condition
C51.9 is a billable ICD-10-CM diagnosis code for malignant neoplasm of vulva, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 731 through 733, 754 through 756. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Female reproductive system cancers - vulva.
For Medicare Advantage risk adjustment, C51.9 maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers) under the V28 model, adding a risk factor of about 0.363 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C51.9 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adenocarcinoma of anogenital mammary-like glands
- Adnexal carcinoma of vulva
- Anogenital verrucous carcinoma of Buschke-Löwenstein
- Basal cell carcinoma of vulva
- Carcinoma of vulva
- FIGO stage finding for vulvar melanoma
- FIGO VM stage V
- Infective dermatosis of female genitalia
- Invasive vulval Paget's disease
- Malignant melanoma of perineum
- Malignant melanoma of skin of perineum
- Malignant melanoma of skin of vulva
- Malignant melanoma of vulva
- Malignant neoplasm of vulva
- Paget's disease of vulva
- Primary adenocarcinoma of vulva
- Primary adnexal carcinoma of vulva
- Primary extramammary Paget disease of skin
- Primary invasive vulval Paget disease
- Primary malignant neoplasm of vulva
- Primary Paget disease of vulva
- Recurrent primary malignant neoplasm of vulva
- Sarcoma of vulva
- Squamous cell carcinoma of anogenital area
- Squamous cell carcinoma of vulva
- Squamous cell carcinoma of vulva due to lichen sclerosus
- Vulval verrucous carcinoma of Buschke-Löwenstein
- Vulvovaginal rhabdomyosarcoma
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C51.9: its own notes plus those printed at C51, block C51-C58, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- malignant neoplasm of skin of female genital organs
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Malignant neoplasm of external female genitalia NOS
- Malignant neoplasm of pudendum
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C51.9, its category, or a range that includes it.
Applicable To 2
These notes mention C51.9.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Malignant Vulvar Neoplasm
a primary or metastatic malignant neoplasm involving the vulva.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| fourchette | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| labia (skin) | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| labium (skin) | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| mons › pubis | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| mons › veneris | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| pudenda, pudendum (femaie) | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| skin NOS › female genital organs (external) | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| skin NOS › female genital organs (external) › labium NEC | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| skin NOS › female genital organs (external) › pudendum | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| skin NOS › female genital organs (external) › vulva | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| skin NOS › vulva | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
| vulva | C51.9 | C79.82 | D07.1 | D28.0 | D39.8 | D49.59 |
Patient EducationClinical
Vulvar Cancer
Vulvar cancer is a rare type of cancer. It forms in a woman's external genitals, called the vulva. The cancer usually grows slowly over several years. First, precancerous cells grow on vulvar skin. This is called vulvar intraepithelial neoplasia (VIN), or dysplasia. Not all VIN cases turn into cancer, but it is best to treat it early.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C51.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C51.9Overview
What is the ICD-10 code for malignant neoplasm of vulva, unspecified?
The ICD-10-CM code for malignant neoplasm of vulva, unspecified is C51.9 (sometimes written as C519). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C51.9 (Malignant neoplasm of vulva) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of vulva, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C51.9 group to?
When malignant neoplasm of vulva, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 732, 755, 756, 754, 733, 731, with relative weights from 0.8583 to 3.5462 depending on complications. Higher weights mean higher Medicare reimbursement.
Can C51.9 be reported with D07.1?
Not as a rule. The Excludes1 note at C51, which applies to C51.9, lists "carcinoma in situ of vulva (D07.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What is the ICD-9 equivalent of C51.9?
Under the General Equivalence Mappings, malignant neoplasm of vulva, unspecified converts to ICD-9-CM 184.4 (malign neopl vulva NOS). The mapping is a direct match.
What HCC is C51.9?
C51.9 (malignant neoplasm of vulva, unspecified) maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers), commonly written as HCC 22, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 11 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does C51.9 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C51.9 adds a risk adjustment factor of about 0.363 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.314 to 0.410 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, and HCC 21) supersedes it when both are reported. See the full factor table on the HCC 22 category page.
