2026 ICD-10-CM Diagnosis Code C21Malignant neoplasm of anus and anal canal

ICD-10-CM Codes›C00–D49›C15-C26›C21

ICD-10-CM C21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C21 is a non-billable ICD-10-CM category code for malignant neoplasm of anus and anal canal, so it cannot be submitted on claims. Use a more specific code from this category instead, such as C21.0, C21.1, C21.2, and C21.8.

Code Identity

ICD-10-CM Code
C21
Billable Status
No — Non-Billable Category
Code Describes
Malignant neoplasm of anus and anal canal
Chapter
C15-C26
Malignant neoplasms of digestive organs

Code Classification

ChapterC00–D49Neoplasms
SectionC15-C26Malignant neoplasms of digestive organs
CategoryC21Malignant neoplasm of anus and anal canal
This CodeC21Malignant neoplasm of anus and anal canal

Specific Coding for Malignant neoplasm of anus and anal canalOverview

Non-specific codes like C21 require more characters. Use one of these billable codes instead:

  • Use C21.0 for Malignant neoplasm of anus, unspecified

  • Use C21.1 for Malignant neoplasm of anal canal

  • Use C21.2 for Malignant neoplasm of cloacogenic zone

  • Use C21.8 for Malignant neoplasm of overlapping sites of rectum, anus and anal canal

Tabular List NotesGuidance

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

Type 2 Excludes

Patient EducationClinical

Anal Cancer

Your anus is the opening at the end of your large intestine. It is where stool (poop) leaves your body. The anus is formed partly from your outer layers of skin and partly from your intestine. Anal cancer is a type of cancer that forms in the tissues of your anus.

The full article covers:

  • What is anal cancer?
  • Who is more likely to develop anal cancer?
  • What are the symptoms of anal cancer?
  • How is anal cancer diagnosed?
  • What are the treatments for anal cancer?
  • Can anal cancer be prevented?

Read the full article at MedlinePlus

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

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 C21Overview

Is C21 (Malignant neoplasm of anus and anal canal) a billable code?

No. This is a category header that groups the codes for malignant neoplasm of anus and anal canal, and headers cannot be submitted on claims. Claims for malignant neoplasm of anus and anal canal need a more specific code from this category, such as C21.0, C21.1, and C21.2.