C79.81

HCC Category Mapping

What This Code Means

Cancer that has spread to the breast tissue from a cancer that originated elsewhere in the body.

Coding Tips

• •This code represents metastatic disease to the breast; do not confuse with primary breast cancer (C50 codes).
• •Always code the primary malignancy site first before this secondary cancer code.

Clinical Significance

Secondary malignant neoplasm of the breast indicates cancer has metastasized to the breast tissue from a primary cancer elsewhere. This is an uncommon scenario since the vast majority of breast malignancies are primary. Metastatic disease to the breast most often comes from contralateral breast cancer, lymphoma, lung cancer, or melanoma. Accurate distinction is critical since treatment for metastatic disease to the breast differs fundamentally from primary breast cancer management.

Documentation Requirements

• ✓Primary cancer site documented and coded separately
• ✓Pathological confirmation that the breast lesion represents metastatic disease, not a new primary
• ✓Immunohistochemistry panel comparing histology to the known primary site
• ✓Imaging — mammography, ultrasound, or MRI showing the breast lesion
• ✓Laterality and location within the breast

Commonly Confused Codes