C21Header code — not billable

Malignant neoplasm of anus and anal canal

Chapter
2. Neoplasms
Category
C21
Effective date
October 1, 2026

Related codes in category C21

C21.0Malignant neoplasm of anus, unspecifiedYesC21.1Malignant neoplasm of anal canalYesC21.2Malignant neoplasm of cloacogenic zoneYesC21.8Malig neoplasm of ovrlp sites of rectum, anus and anal canalYes

Frequently asked questions

What is ICD-10 code C21?

C21 is an ICD-10-CM diagnosis code for Malignant neoplasm of anus and anal canal.

Is C21 a billable code?

No. C21 is a category/header code, not billable on its own — use one of its more specific child codes instead.

What ICD-10-CM chapter is C21 in?

C21 falls under Chapter 2: Neoplasms.

When did C21 become effective?

C21 has been effective since October 1, 2026, per the CMS/CDC ICD-10-CM annual release.

What other codes are related to C21?

C21 belongs to category C21, which includes 4 other codes — see the related codes list on this page.

ICD-10-CM data maintained by CDC/CMS (public domain). Always verify codes with authoritative sources before making coding or billing decisions.