What Mammograms Show Us

What Radiologists Look for on a Mammogram

Mammograms are read (interpreted) by radiologists – doctors that specialize in diagnosing and treating diseases and injuries using medical imaging techniques such as X-rays. When possible, the doctor reading your mammogram will compare it to your previous mammograms. This helps the doctor find small changes that could be signs of cancer. The doctor reading your mammogram will look for different types of changes:

Calcifications: Tiny mineral deposits within the breast tissue. They look like small white spots on a mammogram. They may or may not be caused by cancer. There are 2 types of calcifications:

  • Macrocalcifications: Coarse (larger) calcium deposits that are most likely due to changes in the breasts caused by aging of the breast arteries, old injuries, or inflammation. These deposits are related to non-cancerous conditions and do not require a biopsy. Macrocalcifications are found in about half the women over 50, and in 1 of 10 women under 50.
  • Microcalcifications: Tiny specks of calcium in the breast. Microcalcifications seen on a mammogram are of more concern than macrocalcifications, but they 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 cases, the presence of microcalcifications does not mean a biopsy is needed. But if the microcalcifications have a suspicious look and pattern, a biopsy will be recommended. (During a biopsy, the doctor removes a small piece of the suspicious area to be looked at under a microscope. A biopsy is the only way to tell if cancer is really present.)

Mass: A mass, 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), but may sometimes be a sign of cancer.

Cysts can be simple fluid-filled sacs (known as simple cysts) or can be partially solid (known as complex cystic and solid masses). Simple cysts are benign (not cancer) and don’t need to be biopsied. If a mass is not a simple cyst, it is of more concern and might need to be biopsied to be sure it isn’t cancer.

A cyst and a tumor can feel the same 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’s at least partly solid), more imaging tests may be needed. Some masses can be monitored with regular mammograms or ultrasound, while others may need a biopsy. The size, shape, and margins (edges) of the mass may help the radiologist determine if cancer is likely to be present.

Having your prior mammograms available for the radiologist is very important. They can help show that a mass or calcification has not changed for many years. This would mean that it’s likely not cancer and a biopsy is not needed.

Breast density: Your mammogram report will also contain an assessment of breast density. Breast density is based on how fibrous and glandular tissues are distributed in your breast, vs. how much of your breast is made up of fatty tissue.

Dense breasts are not abnormal, but they are linked to a higher risk of breast cancer. We know that dense breast tissue can make it more difficult to find cancers on a mammogram. Still, experts do not agree on what additional tests, if any, should be done for women with dense breasts who aren’t in a high-risk group (based on gene mutations, breast cancer in the family, or other factors).