Human: My doctor says I have to have a mammogram. What is a mammogram and why is it so important? Assistant: 
A mammogram is an X-ray of the breast. It’s used to detect early signs of breast cancer. The goal of a mammogram is to find any changes in the breast tissue that could be caused by cancer. If you have symptoms such as a lump, pain, or discharge from your nipple, you should see your doctor right away.