ICD-10 Code C21 – Malignant neoplasm of anus and anal canal (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C21 – Malignant neoplasm of anus and anal canal
What it is
C21 identifies a malignant tumor arising in the anus or anal canal. Use it when documentation states cancer in this anatomic site and no more specific subsite or histology is provided.
Clinical signs
Clinical features may include rectal bleeding, anal pain, a palpable mass, or change in bowel habits. Clinical features vary; refer to documentation.
When to use this code
Use C21 when the clinician documents primary malignancy of the anus or anal canal and the record does not specify a different, more exact ICD-10 site code. It is appropriate for confirmed cancer diagnoses, pathology-supported findings, or oncology follow-up notes that identify this primary site.
Do not use for
Do not use it for benign anal lesions, hemorrhoids, or inflammatory anorectal disease. If the documentation names a different primary site or metastatic disease only, check documentation.
Coding tip
Code the most specific anal subsite available, and verify whether the record describes anus, anal canal, or another colorectal location.