A mammogram (a x-ray of the breast) in women who have no signs of breast cancer . It usually involves two x-rays of each breast. The aim of a screening mammogram is to detect a tumor that cannot be felt. Most mammography facilities have switched to “digital” mammography, just as most photographers have switched to digital cameras. The advantages are in ease of storage, and of manipulating the image for interpreting them. For example, the image can be made darker or lighter, or the black and white can be “inverted”, or the image can be greatly magnified. Use of digital mammography has simplified the process for the patient, since it is much less often necessary to do them over.

As regards cancer, the extent of a cancer, especially whether the disease has spread from the original site to other parts of the body. Doctors determine the size of the tumor in its original location, whether there is any cancer seen in the lymph nodes that are nearby, and whether there is any evidence of cancer that has spread from the original site to elsewhere in the body. We have an entire page devoted to breast cancer staging.
Another word used to describe cancer cells is the grade. It is very easy to confuse these two terms, so you might want to look at this definition as well, to be sure you don’t mix them up.