2026 ICD-10-CM Diagnosis Code C21.2Malignant neoplasm of cloacogenic zone

ICD-10-CM Codes›C00–D49›C15-C26›C21

ICD-10-CM C21.2
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C21.2 is a billable ICD-10-CM diagnosis code for malignant neoplasm of cloacogenic zone. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 374 through 376. Coders also document this condition as anal mucosa finding. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Gastrointestinal cancers - anus.

Code Identity

ICD-10-CM Code
C21.2
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of cloacogenic zone
Short Description
Malignant neoplasm of cloacogenic zone
Same as the full description in the CMS dataset.
Parent Code
C21
Malignant neoplasm of anus and anal canal

Code Classification

ChapterC00–D49Neoplasms
SectionC15-C26Malignant neoplasms of digestive organs
CategoryC21Malignant neoplasm of anus and anal canal
This CodeC21.2Malignant neoplasm of cloacogenic zone

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anal mucosa finding
  • Malignant neoplasm of cloacogenic zone
  • Primary cloacogenic carcinoma of anal canal
  • Primary malignant neoplasm of anal canal
  • Primary malignant neoplasm of cloacogenic zone

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.

    • Carcinoma(malignant)
      • cloacogenic
        • unspecified site

Clinical ClassificationClinical

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

CCSR NEO016
Gastrointestinal cancers - anus
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
anus, anal › cloacogenic zoneC21.2C78.5D01.3D12.9D37.8D49.0
cloacogenic zoneC21.2C78.5D01.3D12.9D37.8D49.0

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.

Convert C21.2 to ICD-9-CMHistory

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

ICD-9-CM
154.8 Mal neo rectum/anus NEC
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 C21.2Overview

Is C21.2 (Malignant neoplasm of anus and anal canal) a billable code?

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

What MS-DRG does C21.2 group to?

When malignant neoplasm of cloacogenic zone is the principal diagnosis on an inpatient stay, it groups to MS-DRG 374, 375, 376, with relative weights from 0.9243 to 2.1387 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C21.2?

Under the General Equivalence Mappings, malignant neoplasm of cloacogenic zone converts to ICD-9-CM 154.8 (mal neo rectum/anus NEC). 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.