C21: Malignant neoplasm of anus and anal canal
Codes under C21 (Malignant neoplasm of anus and anal canal). A ✓ marks a billable (fully specified) code; category codes without a ✓ are not billable on their own.
| Code | Description | Billable |
|---|---|---|
| C21.0 | Malignant neoplasm of anus, unspecified | ✓ |
| C21.0 | Malignant neoplasm of anus, unspecified | ✓ |
| C21.1 | Malignant neoplasm of anal canal | ✓ |
| C21.1 | Malignant neoplasm of anal canal | ✓ |
| C21.2 | Malignant neoplasm of cloacogenic zone | ✓ |
| C21.2 | Malignant neoplasm of cloacogenic zone | ✓ |
| C21.8 | Malignant neoplasm of overlapping sites of rectum, anus and anal canal | ✓ |
| C21.8 | Malignant neoplasm of overlapping sites of rectum, anus and anal canal | ✓ |
Frequently asked questions
What is ICD-10-CM code C21?
C21 is an ICD-10-CM category covering Malignant neoplasm of anus and anal canal. It contains 8 more specific diagnosis codes, 8 of which are billable.
Is C21 a billable code?
No — C21 is a category header and isn't billable on its own. Code to the highest level of specificity using one of its subcodes (for example C21.0 — Malignant neoplasm of anus, unspecified). 8 of the 8 codes under C21 are billable.
What codes fall under C21?
C21 includes C21.0, C21.0, C21.1, C21.1, C21.2, plus 3 more. See the full list with descriptions and billable status above.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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