2026 ICD-10-CM Diagnosis Code C43.51Malignant melanoma of anal skin

ICD-10-CM Codes›C00–D49›C43-C44›C43

ICD-10-CM C43.51
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C43.51 is a billable ICD-10-CM diagnosis code for malignant melanoma of anal skin. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 595 through 596. Coders also document this condition as malignant melanoma of anus. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Skin cancers - melanoma.

Code Identity

ICD-10-CM Code
C43.51
Billable Status
Yes — Valid for Submission
Code Describes
Malignant melanoma of anal skin
Short Description
Malignant melanoma of anal skin
Same as the full description in the CMS dataset.
Parent Code
C43.5
Malignant melanoma of trunk

Code Classification

ChapterC00–D49Neoplasms
SectionC43-C44Melanoma and other malignant neoplasms of skin
CategoryC43Malignant melanoma of skin
This CodeC43.51Malignant melanoma of anal skin

Quality Payment Program MeasuresBilling

Medicare quality measures that can apply when C43.51 is part of the patient record.

Melanoma Reporting

High Priority: YES

Measure Type: Process

Submission Methods: Claims, Registry

Description: Pathology reports for primary malignant cutaneous melanoma that include the pT category, thickness, ulceration and mitotic rate, peripheral and deep margin status and presence or absence of microsatellitosis for invasive tumors.

View Measure

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Malignant melanoma of anus
  • Malignant melanoma of perianal skin
  • Malignant melanoma of perineum
  • Malignant melanoma of skin of anus
  • Malignant melanoma of skin of perineum
  • Primary malignant melanoma of anus

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Malignant melanoma of anal margin
  • Malignant melanoma of perianal skin

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Melanoma(malignant)
      • skin
        • anus, anal (skin)
    • Melanoma(malignant)
      • skin
        • perianal skin
    • Melanoma(malignant)
      • skin
        • perineum

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO025
Skin cancers - melanoma
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Melanoma

Melanoma is the most serious type of skin cancer. Often the first sign of melanoma is a change in the size, shape, color, or feel of a mole. Most melanomas have a black or black-blue area. Melanoma may also appear as a new mole. It may be black, abnormal, or "ugly looking."

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C43.51 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
172.5 Malig melanoma trunk
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C43.51Overview

Is C43.51 (Malignant melanoma of trunk) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant melanoma of anal skin on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C43.51 group to?

When malignant melanoma of anal skin is the principal diagnosis on an inpatient stay, it groups to MS-DRG 595, 596, with relative weights from 1.0825 to 2.1207 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C43.51?

Under the General Equivalence Mappings, malignant melanoma of anal skin converts to ICD-9-CM 172.5 (malig melanoma trunk). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.