ICD-10 Code C44.521 – Squamous cell carcinoma of skin of breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C44.521 – Squamous cell carcinoma of skin of breast
What it is
This code identifies a squamous cell carcinoma arising in the skin of the breast. It is used for a malignant skin tumor on the breast surface, not for cancer originating in breast tissue.
Clinical signs
Typical findings include a persistent scaly or crusted skin lesion, a nonhealing ulcer, or a firm enlarging nodule. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents squamous cell carcinoma of the skin located on the breast. It may also apply when pathology confirms cutaneous SCC of the breast skin. Check documentation to ensure the lesion is skin-based and not a breast parenchymal malignancy.
Do not use for
Do not use it for carcinoma of the breast itself, metastatic disease to the breast skin, or an unspecified skin cancer site. Check documentation if the record does not clearly identify the breast skin as the primary site.
Coding tip
Verify that the note specifies “skin of breast” and not breast tissue, since site wording determines whether C44.521 is correct.