Malignant melanoma of anal skin

This code signifies a primary cancerous growth of melanocytes, the pigment-producing cells, originating in the skin of the anus. This is a rare but aggressive form of skin cancer that can spread to other parts of the body.

Apply this code when documentation confirms a primary malignant melanoma specifically located on the anal skin. This diagnosis is typically established through biopsy and histopathological examination. Use this code for initial diagnosis and subsequent encounters related to the primary tumor.

• Differentiate from melanoma of the anal canal (C21.1) or perianal skin (C43.59), as these are distinct anatomical sites.
• Ensure documentation specifies "anal skin" to avoid confusion with other anorectal melanoma sites.
• Always sequence this code as the primary diagnosis when it is the reason for the encounter, unless a complication or metastasis is being treated.