C51.9 (Malignant neoplasm of vulva, unspecified) compared with D49.59 (Neoplasm of unspecified behavior of other genitourinary organ), from the official CMS tabular data. C51.9 and D49.59 name the same anatomical site (fourchette) with a different neoplasm behavior.
Same anatomical site, different neoplasm behavior.
Same site — primary malignancy (fourchette)
The behavior documented for the site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column of the neoplasm table, and therefore which code, applies.
Source: CMS Table of Neoplasms
Same site, different neoplasm behavior. D49.59 and C51.9 name the same anatomical site (fourchette) with a different neoplasm behavior.
From the CMS Table of Neoplasms: the behavior documented for that site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column, and therefore which code, applies.
| C51.9Malignant neoplasm of vulva, unspecified | D49.59Neoplasm of unspecified behavior of other genitourinary organ | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms | C00-D49 — Neoplasms |
| Definition | Malignant neoplasm of vulva, unspecified is a billable ICD-10-CM diagnosis code (C51.9). | Neoplasm of unspecified behavior of other genitourinary organ is a billable ICD-10-CM diagnosis code (D49.59). |
| Includes | malignant neoplasm of skin of female genital organs Malignant neoplasm of external female genitalia NOS Malignant neoplasm of pudendum | 'growth' NOS neoplasm NOS new growth NOS tumor NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources