A biopsy is a diagnostic test to detect and determine important information about your possible cancer. Whenever possible, the surgeon tries to remove all of the malignant breast tissue during a biopsy. Laboratory tests are conducted on the removed tissue to determine whether this was successful.

If all of the malignant breast tissue is removed, the procedure is also called a lumpectomy. Lumpectomy is usually the first treatment of malignant tissue in the breast.

Only the cancerous lump itself and a thin margin of outside tissue is removed.