C21 ICD-10-CM Code: Malignant neoplasm of anus and anal canal
C21 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)
C21
Header CodeICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of anus and anal canal
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C21. Check the code and parent instructions in the Code Book.
Excludes 2
Official- 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)
- gastrointestinal stromal tumors (C49.A-)Inherited from C15-C26
Related Codes
Includes
OfficialNo Includes notes are included in this display for C21. Check the code and parent instructions in the Code Book.
Excludes 1
Official- Kaposi's sarcoma of gastrointestinal sites (C46.4)Inherited from C15-C26
Code First
OfficialNo Code First sequencing instructions are included in this display for C21. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C21. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C21. Check the code and parent instructions in the Code Book.
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
- Code
- C21
- Description
- Malignant neoplasm of anus and anal canal
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- No
- Payment year
- 2026
Coder workflow notes
Get the V28 mapping + MEAT cheat sheet
One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.
Free PDF. No card. Unsubscribe anytime.
What This Code Means
C21 is the ICD-10-CM diagnosis code for malignant neoplasm of anus and anal canal. C21 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of digestive organs (c15-c26).
Header codes like C21 cannot be reported on claims directly; they organize child codes that share clinical context. Coders should select the billable child code that matches the documented presentation and then verify its current source-backed HCC mapping. Do not infer a child code or risk adjustment value from the header alone.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for C21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Excludes 2, Not included here, may code separately
- 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)