There are several types of tests that can be done to visualize the breast tissue in a woman who is suspected of having breast cancer. A mammogram is an x-ray that is used to screen (or look for) for breast cancer. It is also used to evaluate the breast in a woman has a lump in her breast. Other common tests used to visualize the breast tissue include ultrasound and MRI. If an abnormality is discovered on physical exam and/or an imaging study, a biopsy is performed. A biopsy involves the removal of a small amount of the abnormal breast tissue using a needle. This allows the doctor to evaluate the cells under the microscope to determine whether abnormal/cancerous cells exist.