Metastatic breast cancer is also classified as Stage 4 breast cancer, also known as MBC, stage IV or Advanced Breast Cancer, is cancer that has spread beyond the breast and lymph nodes under the arm. The most common sites of metastases are the bones, lungs, liver and brain.
No one dies from breast cancer that remains in the breast. The lump itself is not what kills. The spread of cancerous cells to a vital organ is what kills. This is called metastasis.