A Core Needle Breast Biopsy is a medical test which can identify the cause of an abnormal lump or calcification in the breast. A radiologist performs this procedure in the radiology department. During the procedure, the radiologist inserts a needle into the abnormal area under the imaging guidance (ultrasound or X-ray) and removes a sample of the tissue, which is given to a pathologist, who looks at it under a microscope. The pathologist can determine what the abnormal tissue is: cancer, non-cancerous tumor, infection, or scar.