ICD-10-CM Code C21.1

Malignant neoplasm of anal canal

Version 2020 Billable Code Neoplasm Malignant Primary

Valid for Submission

C21.1 is a billable code used to specify a medical diagnosis of malignant neoplasm of anal canal. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code C21.1 might also be used to specify conditions or terms like adenocarcinoma of anal canal, adenocarcinoma of anus, anal canal tnm finding, anal canal tnm finding, anal canal tnm finding, anal canal tnm finding, etc

The following anatomical sites found in the Table of Neoplasms apply to this code given the correct histological behavior: anus, anal canal ; anus, anal sphincter ; canal ; canal anal ; hemorrhoidal zone ; sphincter ; sphincter anal ; etc

Short Description:Malignant neoplasm of anal canal
Long Description:Malignant neoplasm of anal canal

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code C21.1:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Malignant neoplasm of anal sphincter


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Adenocarcinoma of anal canal
  • Adenocarcinoma of anus
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anal canal TNM finding
  • Anorectal adenocarcinoma
  • Carcinoma of anal canal
  • Carcinoma of anus
  • Carcinoma of anus
  • Carcinoma of anus
  • Extramammary Paget's disease of skin
  • Malignant melanoma of anus
  • Malignant tumor of anal canal
  • Malignant tumor of anus and anal canal
  • Paget disease of anal canal
  • pN1: Metastasis in perirectal lymph node
  • pN2: Metastasis in unilateral internal iliac AND/OR inguinal lymph node
  • pN3: Metastasis in perirectal and inguinal lymph nodes AND/OR bilateral internal iliac AND/OR inguinal lymph nodes
  • Primary malignant melanoma of anal canal
  • Primary malignant melanoma of anus
  • Primary malignant neoplasm of anal canal
  • Primary malignant neoplasm of skin of perineum
  • Primary squamous cell carcinoma of anal canal
  • Primary squamous cell carcinoma of anus
  • pT1: Tumor 2 cm or less in greatest dimension
  • pT2: Tumor more than 2 cm but not more than 5 cm in greatest dimension
  • pT3: Tumor more than 5 cm in greatest dimension
  • pT4: Tumor of any size invades adjacent organ

Diagnostic Related Groups

The ICD-10 code C21.1 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2019 through 09/30/2020.


Convert C21.1 to ICD-9

  • 154.2 - Malig neopl anal canal

Code Classification

  • Neoplasms (C00–D48)
    • Malignant neoplasms of digestive organs (C15-C26)
      • Malignant neoplasm of anus and anal canal (C21)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Table of Neoplasms

The code C21.1 is included in the table of neoplasms by anatomical site. For each site there are six possible code numbers according to whether the neoplasm in question is malignant, benign, in situ, of uncertain behavior, or of unspecified nature. The description of the neoplasm will often indicate which of the six columns is appropriate.

Where such descriptors are not present, the remainder of the Index should be consulted where guidance is given to the appropriate column for each morphological (histological) variety listed. However, the guidance in the Index can be overridden if one of the descriptors mentioned above is present.

Neoplasm, neoplastic Malignant
CaInSitu Benign Uncertain
»anus, anal
»anus, anal
»hemorrhoidal zone

Information for Patients

Anal Cancer

The anus is where stool leaves your body when you go to the bathroom. It is made up of your outer layers of skin and the end of your large intestine. Anal cancer is a disease in which cancer cells form in the tissues of the anus.

Anal cancer is rare. It is more common in smokers and people over 50. You are also at higher risk if you have HPV, have anal sex, or have many sexual partners.

Symptoms include bleeding, pain, or lumps in the anal area. Anal itching and discharge can also be signs of anal cancer.

Doctors use tests that examine the anus to diagnose anal cancer. They include a physical exam, endoscopy, ultrasound, and biopsy.

Treatments include radiation therapy, chemotherapy, and surgery.

NIH: National Cancer Institute

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