Question: How does the doctor know that my breast is the primary site of my cancer?
Answer: Well, typically we look under the microscope at the cells that were biopsied. And usually these cells have very characteristic patterns. Sometimes we use markers that are expressed in breast cancer cells as opposed to other types of tumors. If we biopsy, for example, a nodule someplace else outside of the breast then we can use these characteristics to differentiate between breast cancer that has spread versus those that are from other organs. We also use the characteristics that are seen on mammogram and ultrasound and other scanning techniques that give us a good idea that this is a breast cancer.