When a doctor reads your mammogram, he or she will look for several types of changes.
According to the American Cancer Society, the doctor may look for calcifications, which are tiny mineral deposits within the breast tissue that appear as small white spots on the films. They may or may not be caused by cancer. There are two types of calcifications:
Macrocalcifications are coarse (larger) calcium deposits that most likely represent degenerative changes in the breasts, such as aging of the breast arteries, old injuries, or inflammation. These deposits are associated with benign (non-cancerous) conditions and do not require a biopsy. Microcalcifications are found in about half the women over the age of 50, and in about 1 in 10 women younger than 50.
Microcalcifications are tiny specks of calcium in the breast. They may appear alone or in clusters. Microcalcifications seen on a mammogram are of more concern, but do not always mean that cancer is present. The shape and layout of microcalcifications help the radiologist judge how likely it is that cancer is present.
In most instances, the presence of microcalcifications does not mean a biopsy is needed. If the microcalcifications look suspicious for cancer, a biopsy will be done.
A mass, which may occur with or without calcifications, is another important change seen on a mammogram. Masses are areas that look abnormal and they can be many things, including cysts (non-cancerous, fluid-filled sacs) and non-cancerous solid tumors (such as fibroadenomas).
Cysts can be simple fluid-filled sacs (known as simple cysts) or can be partially solid (known as complex cysts). Simple cysts are benign and don't need to be biopsied.
Any other type of mass (such as a complex cyst or a solid tumor) might need to be biopsied to be sure it isn't cancer.
A cyst and a tumor can feel alike on a physical exam. They can also look the same on a mammogram. To confirm that a mass is really a cyst, a breast ultrasound is often done. Another option is to remove (aspirate) the fluid from the cyst with a thin, hollow needle.
If a mass is not a simple cyst (that is, if it is at least partly solid), then you may need to have more imaging tests. Some masses can be watched with periodic mammograms, while others may need a biopsy. The size, shape, and margins (edges) of the mass help the radiologist to determine if cancer may be present.
Having your previous mammograms available for the radiologist is very important. They can be helpful to show that a mass or calcification has not changed for many years. This would mean that it is probably a benign condition and a biopsy is not needed.
Computer-aided detection and diagnosis
Over the past two decades, computer-aided detection and diagnosis (CAD) has been developed to help radiologists detect suspicious changes on mammograms. This can be done with standard film mammograms or with digital mammograms.
Computers can help doctors identify abnormal areas on a mammogram by acting as a second set of "eyes." For standard mammograms, the film is fed into a machine, which converts the image into a digital signal that is then analyzed by the computer. Alternatively, the technology can be applied to a digital mammogram. The computer then displays the image on a video screen, with markers pointing to areas it "thinks" the radiologist should check especially closely.
Although some doctors find CAD helpful, the results of two large studies found that it did not find more cancers or find cancers earlier. It did, however, increase the number of women who needed to come back for more tests and/or have breast biopsies. Whether CAD will continue to be used in the future is not clear.