Needle biopsy is a medical test performed by interventional radiologists to identify the cause of a lump or mass, or other abnormal condition in the body. During the procedure, the doctor inserts a small needle, guided by X-ray or other imaging techniques, into the abnormal area. A sample of tissue is removed and given to a pathologist who looks at it under a microscope to determine what the abnormality is -- for example, cancer, a noncancerous tumor, infection, or scar.