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  6. 2025 ICD-10-CM Code C21
Version 2025
Non-Billable Code

2025 ICD-10-CM Diagnosis Code C21

Malignant neoplasm of anus and anal canal

ICD-10-CM Code:
C21
ICD-10 Code for:
Malignant neoplasm of anus and anal canal
Is Billable?
Not Valid for Submission
Code Navigator:

C21 is a non-specific and non-billable diagnosis code code, consider using a code with a higher level of specificity for a diagnosis of malignant neoplasm of anus and anal canal. The code is not specific and is NOT valid for the year 2025 for the submission of HIPAA-covered transactions. Category or Header define the heading of a category of codes that may be further subdivided by the use of 4th, 5th, 6th or 7th characters.

Specific Coding Applicable to Malignant neoplasm of anus and anal canal

Non-specific codes like C21 require more digits to indicate the appropriate level of specificity. Consider using any of the following ICD-10-CM codes with a higher level of specificity when coding for malignant neoplasm of anus and anal canal:

  • Use C21.0 for Malignant neoplasm of anus, unspecified - BILLABLE CODE

  • Use C21.1 for Malignant neoplasm of anal canal - BILLABLE CODE

  • Use C21.2 for Malignant neoplasm of cloacogenic zone - BILLABLE CODE

  • Use C21.8 for Malignant neoplasm of overlapping sites of rectum, anus and anal canal - BILLABLE CODE

Code Classification

  • Neoplasms
    (C00–D49)
    • Malignant neoplasms of digestive organs
      (C15-C26)
      • Malignant neoplasm of anus and anal canal
        (C21)

Tabular List of Diseases and Injuries

The following annotation back-references are applicable to this diagnosis code. The Tabular List of Diseases and Injuries is a list of ICD-10-CM codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more.


Type 2 Excludes

Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

Patient Education


Anal Cancer

What is anal cancer?

Your anus is the opening at the end of your large intestine. It is where stool (poop) leaves your body. The anus is formed partly from your outer layers of skin and partly from your intestine. Anal cancer is a type of cancer that forms in the tissues of your anus.

Who is more likely to develop anal cancer?

Anyone can get anal cancer, but you are more likely to develop it if you:

  • You have an infection with high-risk HPV, especially if you have certain types. Most anal cancers are related to HPV infection.
  • Have a weakened immune system, from conditions such as HIV or because of medicines you need to take after an organ transplant.
  • Have had vulvar, vaginal, or cervical cancer.
  • Have many sexual partners.
  • Have anal sex.
  • Smoke cigarettes.

What are the symptoms of anal cancer?

The signs and symptoms of anal cancer may include:

  • Bleeding from the anus or rectum
  • A lump near the anus
  • Pain or pressure in the area around the anus
  • Itching or discharge from the anus
  • A change in bowel habits, such as narrower stools, having to go more often, or bowel incontinence

How is anal cancer diagnosed?

To find out if you have anal cancer, your provider:

  • Will take your medical history, which includes asking about your symptoms.
  • Will ask about your family health history.
  • May do a digital rectal examination (DRE). A DRE is an exam of the anus and rectum. For the exam, your provider will insert a lubricated, gloved finger into the lower part of your rectum to feel for lumps or anything else that seems unusual.
  • May order tests that examine the anus and rectum, such as:
    • An anoscopy, an exam of the anus and lower rectum using a short, lighted tube called an anoscope. There is also a type of anoscopy called a high-resolution anoscopy. It uses a special magnifying device called a colposcope along with the anoscope to view these areas.
    • A proctoscopy, a procedure to look inside the rectum and anus using a thin, tube-like instrument with a light and a lens.
    • An endo-anal or endorectal ultrasound, a procedure in which an ultrasound probe is inserted into the rectum.
  • May do a biopsy during an anoscopy or proctoscopy.

What are the treatments for anal cancer?

The treatments for anal cancer include radiation therapy, chemotherapy, and surgery. Which treatment you get will depend on how advanced the cancer is, your overall health, and your preferences.

Can anal cancer be prevented?

You may be able to lower your risk of getting anal cancer by getting an HPV vaccine and not smoking. Contact your provider if you need help quitting smoking.

It is currently not known if using condoms can prevent anal HPV infections. But using latex condoms every time you have sex can help prevent HIV, a risk factor for anal cancer. And they also help prevent other sexually transmitted infections (STIs). If your or your partner is allergic to latex, you can use polyurethane condoms.

If you are an adult with HIV, it's important to get an anal cancer screening every year. The screening checks for anything that seems unusual, such as lumps, burning, and precancer cells (cells that could turn into cancer). The screening will include a digital rectal exam. If anything unusual is found, you will have an anoscopy or high resolution anoscopy.


[Learn More in MedlinePlus]

Anal Cancer Treatment (PDQ®)

Learn about anal cancer risk factors, signs and symptoms, tests to diagnose, factors affecting prognosis, staging, and treatment.
[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.