U.S. ICD-10-CM · FY 2027

C21 ICD-10-CM Code: Malignant neoplasm of anus and anal canal

A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.

Code definition

Official description

C21

Malignant neoplasm of anus and anal canal

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where C21 sits

  1. 1

    Chapter 2

    Neoplasms (C00-D49)

  2. 2

    Section

    Malignant neoplasms of digestive organs (C15-C26)

  3. 3

    Category C21

    Malignant neoplasm of anus and anal canal

  4. 4

    Code C21

    Malignant neoplasm of anus and anal canal

More specific choices

Codes under C21

C21 is a non-billable category. Choose the child code that best matches the documented diagnosis.

C21.0

Malignant neoplasm of anus, unspecified

C21.1

Malignant neoplasm of anal canal

C21.2

Malignant neoplasm of cloacogenic zone

C21.8

Malignant neoplasm of overlapping sites of rectum, anus and anal canal

Documentation details

Notes for this code

Inclusion terms

No inclusion terms are listed for C21.

Code first

No “code first” instruction is listed for C21.

Use additional code

No “use additional code” instruction is listed for C21.

Excludes1

Conditions that should not be reported together with this code.

No Excludes1 note is listed for C21.

Excludes2

Conditions not included here that may be reported separately when present.

  • malignant carcinoid tumors of the colon (C7A.02-)
  • malignant melanoma of anal margin (C43.51)
  • malignant melanoma of anal skin (C43.51)
  • malignant melanoma of perianal skin (C43.51)
  • other and unspecified malignant neoplasm of anal margin (C44.500, C44.510, C44.520, C44.590)
  • other and unspecified malignant neoplasm of anal skin (C44.500, C44.510, C44.520, C44.590)
  • other and unspecified malignant neoplasm of perianal skin (C44.500, C44.510, C44.520, C44.590)

Transparency

Source and release

Data release

U.S. ICD-10-CM · FY 2027

Effective date

Oct 1, 2026

Publisher

Vero Scribe Inc.

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code C21 mean?

C21 is the FY 2027 U.S. ICD-10-CM code for “Malignant neoplasm of anus and anal canal.”

Is C21 a billable or specific ICD-10-CM code?

No. C21 has more specific child codes in the FY 2027 reference data. Select the code that matches the documentation and confirm the active code set and payer requirements.

Where is C21 located in ICD-10-CM?

C21 is listed in Chapter 2, Neoplasms (C00-D49), within Malignant neoplasms of digestive organs (C15-C26) (C15–C26), under category C21, Malignant neoplasm of anus and anal canal.

What coding notes are listed for C21?

No inclusion terms are listed for C21 in this reference record. No code-first instruction is listed. No Excludes1 note is listed. Excludes2 notes: malignant carcinoid tumors of the colon (C7A.02-); malignant melanoma of anal margin (C43.51); malignant melanoma of anal skin (C43.51); malignant melanoma of perianal skin (C43.51); other and unspecified malignant neoplasm of anal margin (C44.500, C44.510, C44.520, C44.590); other and unspecified malignant neoplasm of anal skin (C44.500, C44.510, C44.520, C44.590); other and unspecified malignant neoplasm of perianal skin (C44.500, C44.510, C44.520, C44.590).

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