C21.1 – Malignant neoplasm of anal canal

ICD-10-CM 2027 diagnosis code · Malignant neoplasms of digestive organs

Billable code

ICD-10-CM code C21.1

Code: C21.1 (claims format: C211)
Description: Malignant neoplasm of anal canal
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 2. Neoplasms (C00-D49)
Block: C15-C26 Malignant neoplasms of digestive organs
Parent codes: C21

Notes for C21.1

Applicable to:

Malignant neoplasm of anal sphincter

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

C21 – Malignant neoplasm of anus and anal canal

Excludes2 (not included here):

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)

Block C15-C26

Excludes1 (not coded here):

Kaposi's sarcoma of gastrointestinal sites (C46.4)

Excludes2 (not included here):

gastrointestinal stromal tumors (C49.A-)

Related codes in C21

Frequently asked questions

What is ICD-10 code C21.1?

C21.1 is the ICD-10-CM code for malignant neoplasm of anal canal, in the block C15-C26 (Malignant neoplasms of digestive organs).

Is C21.1 a billable code?

Yes. C21.1 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does C21.1 belong to?

It belongs to category C21 – Malignant neoplasm of anus and anal canal.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.