When a mammogram is used to detect cancer in women before they have any signs or symptoms of the disease, is it called a screening mammogram. Screening mammograms consist of two images of each breast, and detect lumps or other abnormalities.
Diagnostic mammograms are used after a lump or other symptoms of the disease have been found. It is also used if it is difficult to see breast tissue in a screening mammogram due to certain circumstances, such as the presence of breast implants. Diagnostic mammography consists of more x-rays than screening mammography and therefore takes longer to complete.
Women should begin scheduling their annual mammograms at the age of 40.
Video from: About.com