Is C21.8 a billable ICD-10-CM code?

Yes. C21.8 is a billable, specific ICD-10-CM code and is valid for submission on a claim.

Where does C21.8 sit in the tabular list?

Neoplasms (C00-D49), in the block Malignant neoplasms of digestive organs (C15-C26).

C21.8

C21.8 — Malignant neoplasm of overlapping sites of rectum, anus and anal canal

Billable / specific codeICD-10-CM

C21.8 is a billable, specific ICD-10-CM code for malignant neoplasm of overlapping sites of rectum, anus and anal canal. It is valid for submission on a claim.

Inclusion terms

Alternative wordings a physician may use in the chart for this same code.

Malignant neoplasm of anorectal junction
Malignant neoplasm of anorectum
Primary malignant neoplasm of two or more contiguous sites of rectum, anus and anal canal

Excludes2 inherited from the categories above C21.8

Also inherited, and the opposite of Excludes1: these conditions are not part of C21.8, but a patient can have both, so you may code both.

Written on C21 — Malignant neoplasm of anus and anal canal

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)

Risk adjustment

C21.8 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

C21.8 is named in 105 Medicare coverage policies — 105 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

A52370Billing and Coding: Bevacizumab and biosimilars
A52450Billing and Coding: Paclitaxel (e.g., Taxol®/Abraxane ™)
A52479Oral Anticancer Drugs - Policy Article
A52479Oral Anticancer Drugs - Policy Article

Code history

C21.8 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.

Related codes at this level

Codes that share C21. If C21.8 is not quite right, the correct code is usually one of these.

Questions about C21.8

Is C21.8 a billable ICD-10-CM code?: Yes. C21.8 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does C21.8 sit in the tabular list?: Neoplasms (C00-D49), in the block Malignant neoplasms of digestive organs (C15-C26).