Screening vs. Diagnostic Mammogram: What's the Difference?

While you may be aware of the recommendation that women should start receiving annual mammograms at age 40, you might not know that mammograms can serve two different purposes. The differences between a screening vs. diagnostic mammogram are implied in their respective names, but the differences go beyond just the procedures.

What Is a Mammogram?

Before discussing the differences between a screening vs. diagnostic mammogram, it's important to understand what a mammogram is and what it does. A mammogram is an X-ray that uses a small amount of radiation to take images of the breast. Each breast is placed between two plates that gently spread and flatten it to be imaged. An image is taken from two views: forward-facing and side-facing. The images can detect any abnormalities or changes in the breast, such as a lump.

A 3D mammogram, also known as breast tomosynthesis, can take multiple images of the breast that are put together into a three-dimensional image that allows the doctor to see the breast tissue more clearly. According to the American Cancer Society, this technique may lower the chances of being called back for a follow-up and may be able to find more cancers. However, not all health insurance providers will cover this type of mammogram.

"Most imaging centers perform a simultaneous 2D and 3D examination. There is software increasingly being used that can create sort of a virtual 2D image that some centers use, so there are places only doing the 3D examination," said Daniel Herron, MD, the director of women's imaging at Mercy Imaging Centers, a service of Dignity Health Medical Foundation. "This likely will be more common in the future as the virtual 2D images become better."

Screening Mammogram

A screening mammogram is used to screen or look for unsuspected breast cancer in women who do not have any symptoms. A screening mammogram takes images of each breast from two different angles. It takes about 10 to 15 minutes, and you will be asked to wait for about five minutes while the X-rays are developed. Results will depend on whether or not more testing needs to be done.

According to the American College of Radiology (ACR), additional or supplementary views may be ordered, but these are not part of the routine screening mammogram, except for women with breast implants. Views may also be modified to accommodate women who have limitations with positioning, the ACR says.

"Generally, as long as you are healthy and would accept treatment for breast cancer, then it is reasonable to perform screening mammography," Dr. Herron said. "There are patients who are not expected to have a very long lifespan for other medical reasons who may not benefit from mammography."

Although the recommended age to begin annual mammograms is 40, patients with a family history of breast cancer may start getting screening mammograms sooner.

"Typically we recommend starting screening 10 years earlier than the age of diagnosis of a first-degree relative, such as a mom or sister, but no earlier than age 30. For example, if the patient's mom was diagnosed at age 41, we typically would recommend starting screening at age 31," Dr. Herron said.

Diagnostic Mammogram

A diagnostic mammogram is used if there are any changes or abnormalities seen on a screening mammogram. A diagnostic mammogram may include extra images or views of the breast that were not included in the screening mammogram. This allows an area of clinical or radiographic concern to be evaluated, according to the ACR. These additional views may include spot compression or spot compression with magnification.

According to the National Breast Cancer Foundation, a diagnostic mammogram may not only find breast tumors that are too small to feel, but it may also detect ductal carcinoma in situ (DCIS). This refers to abnormal cells in the lining of the breast duct that may become invasive breast cancer in some women.

"Additionally, it is customary for the physician radiologist to talk to the patient during the diagnostic exam to give them their results while they are in the imaging center," Dr. Herron said. "Fortunately, in most cases the diagnostic exam will show no breast cancer."

A diagnostic mammogram also takes about 10 to 15 minutes to complete, but can take longer if additional views are performed. A mammogram for a woman with breast implants may take about 30 minutes to ensure that a clear image is taken.

When you receive the results from your mammogram, they'll vary depending on different factors, such as the complexity of the procedure and whether or not more information is needed.

If you have any questions about what to expect from your mammogram, or how you can expect to receive your results, be sure to ask your doctor.