Merkel cell carcinoma of skin of breast

This code identifies a rare and aggressive neuroendocrine carcinoma originating in the skin of the breast. Merkel cell carcinoma is characterized by rapid growth and a high propensity for local recurrence and metastasis. It typically presents as a firm, painless, shiny nodule or plaque.

Use this code when documentation explicitly states a diagnosis of Merkel cell carcinoma located on the skin of the breast. This diagnosis is typically confirmed by biopsy and immunohistochemical staining. Ensure the physician's notes clearly specify the primary site as the skin of the breast.

• Differentiate from other primary breast malignancies (e.g., invasive ductal carcinoma) or metastatic lesions to the breast.
• Confirm the primary site is the skin of the breast, not the underlying breast tissue.
• Code any associated metastatic sites separately, if applicable, using appropriate secondary malignancy codes.