C21.0 — Malignant neoplasm of anus, unspecified
C21.0 is a billable, specific ICD-10-CM code for malignant neoplasm of anus, unspecified. It is valid for submission on a claim.
Other codes that can never be billed with C21.0
These codes carry an Excludes1 note pointing at C21.0. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading C21.0 alone.
- C44.5Other and unspecified malignant neoplasm of skin of trunk
Risk adjustment
C21.0 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:
- HCC 22 Bladder, Colorectal, and Other Cancers0.363 RAF
Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.
Medicare coverage
C21.0 is named in 59 Medicare coverage policies — 59 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A52450Billing and Coding: Paclitaxel (e.g., Taxol®/Abraxane ™)
- A52450Billing and Coding: Paclitaxel (e.g., Taxol®/Abraxane ™)
- A52479Oral Anticancer Drugs - Policy Article
- A52479Oral Anticancer Drugs - Policy Article
How C21.0 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to C21.0.
- Paget's disease›extramammary›anus
Related codes at this level
Codes that share C21. If C21.0 is not quite right, the correct code is usually one of these.
Questions about C21.0
- Is C21.0 a billable ICD-10-CM code?
- Yes. C21.0 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does C21.0 sit in the tabular list?
- Neoplasms (C00-D49), in the block Malignant neoplasms of digestive organs (C15-C26).