C21 – Malignant neoplasm of anus and anal canal

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

Non-billable header

ICD-10-CM code C21

Code: C21 (claims format: C21)
Description: Malignant neoplasm of anus and anal canal
Billable: No – use a more specific code below
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

Billable codes under C21

C21 is a header code and cannot be used on claims. Choose the most specific code:

Notes for C21

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)

Notes inherited from parent codes

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

Block C15-C26

Excludes1 (not coded here):

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

Excludes2 (not included here):

gastrointestinal stromal tumors (C49.A-)

Frequently asked questions

What is ICD-10 code C21?

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

Is C21 a billable code?

No. C21 is a header code with more specific child codes; report one of the billable codes listed above.

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.