Squamous cell carcinoma of anal skin

This code identifies a malignant neoplasm originating from the squamous cells of the skin surrounding the anus. It specifically refers to a type of skin cancer found in the perianal region, distinct from anal canal cancers.

Use this code when documentation clearly specifies squamous cell carcinoma affecting the external anal skin. This diagnosis is typically confirmed by biopsy and pathology reports. It is appropriate for primary diagnoses of this specific malignancy.

• Differentiate carefully between anal skin (perianal) and anal canal squamous cell carcinoma; the latter uses codes from the C21 category.
• Ensure the pathology report explicitly states "squamous cell carcinoma" and specifies the "anal skin" or "perianal skin" as the site.
• Do not use this code for melanoma or other types of skin cancer affecting the anal region.