Mammogram

April 10, 2025

This page was reviewed under our medical and editorial policy by Leah Naghi, M.D., assistant clinical professor, and Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

A mammogram is a type of screening and diagnostic tool that helps to detect and evaluate breast cancer. This test is used to look for breast cancer, even if a woman has no signs or symptoms of the disease, and to assist in understanding whether follow-up testing is needed.

In 2018, about two-thirds of women in the United States aged 40 and older reported having a mammogram within the last two years, according to the U.S. Centers for Disease Control and Prevention’s National Center for Health Statistics. This overall level has been fairly stable since 2008.

What Is a Mammogram?

A mammogram is an imaging test performed by an X-ray technician to take detailed pictures of the inside of the breast. It is performed as an outpatient procedure at a hospital, clinic or doctor’s office in under 30 minutes. To make the images, the test uses an X-ray machine, which delivers radiation in low doses.

A radiologist, trained to read and understand X-ray images, analyzes them and puts together a report.

Radiologists look for different changes or abnormalities in breast tissue on mammograms to help find breast cancer. Some of the changes they look for include:

• Small calcium deposits called calcifications
• Abnormally shaped tissue lumps called masses
• Tissue that looks different from normal tissue, called asymmetries
• Tissue that seems to be pulled abnormally, called architectural distortions

Not every change or abnormality means that a woman has breast cancer. The radiologist will contact the patient’s doctor if the results indicate that further testing is warranted to confirm or rule out the disease.

Types of Mammograms

There is more than one type of mammography. The care team will order the type that is suited for the patient’s situation.

Digital mammograms: These are recorded and stored on computer files and have largely replaced conventional mammography stored on film. This is because digital pictures are easier to enhance and enlarge.

Doctors may also schedule a standard or 3D mammogram.

Standard two-dimensional (2D) mammogram: Here, the breast is pressed onto the X-ray plate from two angles: side to side and top to bottom.

3D mammogram: Also called 3D mammography or digital breast tomosynthesis, in this procedure the X-ray machine moves around the breast in an arc while taking a series of pictures. A computer then compiles these images in “slices,” which gives the radiologist a clearer viewing of the breast tissue. Since it is sometimes hard with standard mammography to see through dense breast tissue (which contains more fibrous and connective tissue than fatty tissue), radiologists may suggest 3D mammograms for women with dense breasts.

The type of mammogram the doctor schedules also depends on whether a woman has symptoms of breast cancer and if signs of the disease are found during a physical exam or previous mammogram.

Screening Versus Diagnostic Mammogram

If a patient does not have signs or symptoms of breast cancer or other issues, a routine screening mammogram is performed. This typically involves taking two or more images of each breast to help find potential tumors or calcifications that may be cancerous.

A diagnostic mammogram is conducted if a patient has signs or symptoms of breast cancer, such as breast or nipple pain, swelling, or skin redness or flaking. Diagnostic mammograms may also be performed:

• If the radiologist sees an abnormal mass or tissue change on the screening mammogram
• If a patient has had a past case of breast cancer
• If a patient has breast implants

Diagnostic mammograms typically include more pictures from more angles than screening mammograms.

Screening and diagnostic mammograms may be either standard or 3D, depending on what the radiologist recommends and each patient’s personal preferences.

Mammogram Versus Ultrasound

Like a mammogram, an ultrasound is an imaging test that may be used to help detect breast cancer. Mammogram pictures are created from X-rays, while ultrasound images are formed by sound waves and their echoes.

How mammograms and ultrasounds compare, listed below.

Breast ultrasound: This is used for breast lumps that may be felt, but are not seen on a mammogram. Screening mammograms, meanwhile, are used to see smaller lumps or changes that are not felt, especially tiny microcalcifications (calcium deposits) that may indicate breast cancer.

Ultrasound: This is used to help tell the difference between a cyst (fluid-filled sac that typically is not cancer) or a solid mass (may or may not be cancer), while a mammogram image does not always provide enough detail to differentiate the two.

Either ultrasound or 3D mammograms may be recommended for women who have dense breast tissue.

Ultrasound and diagnostic mammograms are also used as diagnostic follow-ups when abnormalities are found on a screening mammogram.

There are also certain safety differences between mammograms and ultrasounds.

Are mammograms safe? Mammograms give off low doses of radiation, which is generally considered safe for women who are not pregnant. The doctor will typically recommend other screening or diagnostic options if a woman is pregnant, since the radiation poses a slightly increased risk of harm to the fetus.

Are ultrasounds safe? Because radiation is not given off by ultrasound waves, it is generally considered safe, including for pregnant women.

Mammogram Screening Guidelines

It is important for women to have a discussion with their doctor about when to get a mammogram. Regular screenings have been shown to help find cancer during its early stages when treatment tends to be more successful. The doctor should provide information on risk factors for developing breast cancer, along with the benefits and risks of having mammograms and a recommended screening schedule.

Different organizations offer different mammogram age screening guidelines. The U.S. Preventive Services Task Force (USPSTF) includes doctors and medical experts who provide guidance on breast cancer screenings for disease prevention. The task force recommends women at average risk for developing breast cancer have a mammogram every two years between the ages of 40 and 74.

The American Cancer Society (ACS) recommends the following mammogram screening schedule for women at average risk for developing the disease:

• Every year (optional) between the ages of 40 and 44
• Every year between the ages of 45 and 54
• Every other year from age 55 on, as long as the woman is in good health with a life expectancy of at least 10 years

Some women have genetic or other factors that put them at high risk for developing breast cancer. For women in this category, the ACS recommends having a mammogram every year starting at age 30, along with a breast magnetic resonance imaging (MRI) scan.

What to Expect During the Mammogram Procedure

A mammogram is typically performed by an X-ray technologist, who is the only other person in the room during the procedure. The radiologist reads the images after the appointment.

It is recommended that patients avoid wearing perfumes, deodorants, powders, lotions or other skincare items on their breasts and under their arms on the day of the mammogram, since these may show up as white spots on the images.

Before a mammogram, women should let the technologist know if they are pregnant, breastfeeding or if they have breast implants, recent breast changes or physical issues that prevent them from holding still during the procedure.

Here are the steps for a mammogram:

• The patient undresses from the waist up and stands in front of an X-ray machine.
• The technologist places one breast on a plate on the machine.
• For a standard screening mammogram, an upper plate is lowered to compress (flatten) the breast in order to get a picture angle from top to bottom.
• The patient is asked to move positions, and this procedure is repeated in order to get a picture angle from side to side.
• The radiologist takes these same two pictures of the other breast as well, for a total of four pictures.
• The breast is compressed for about 10 to 15 seconds per picture, and the patient may be asked to hold their breath during that time.
• For a 3D mammogram, the procedure is the same, and the patient may be asked to hold their breath as the machine moves in an arc around the breast to take pictures.
• For a diagnostic mammogram, the technologist usually takes more than two pictures, and they may be focused on an area of concern where symptoms are present or where a screening mammogram showed abnormal tissue.

Do Mammograms Hurt?

Some women describe a mammogram as uncomfortable, and some may feel brief pain while the breast is compressed between the plates of the machine.

The discomfort from a mammogram only lasts a few moments until the compression stops. The level of discomfort depends on a few factors, such as breast size, technologist skill, the amount of compression needed to obtain clear pictures and each woman’s sensitivity level. Patients concerned about pain may ask their care team about taking acetaminophen (Tylenol^®) or ibuprofen (Advil^®, Motrin^®) beforehand.

How Long Does a Mammogram Take?

While a mammogram itself usually only takes a few moments, the entire procedure may last about 20 minutes. Diagnostic mammograms tend to take a little longer than screening mammograms because more images are taken of the breast tissue.

What Do Mammogram Results Mean?

Patients often wonder, what does cancer look like on a mammogram?

Cancer may show up as white spots, abnormal-looking masses or tissue distortions on a mammogram. However, it is important to remember that these abnormal mammogram findings do not always mean that cancer is present. They may be noncancerous (benign) abnormalities or just part of normal tissue patterns.

Mammogram results are sorted into one of seven main Breast Imaging Reporting and Data System (BI-RADS) categories, as listed below.

Category 0: The radiologist’s report is incomplete, and more tests may be needed to determine if an abnormality is present (or a radiologist still needs to compare the patient’s current mammogram with a previous one).

Category 1: Negative abnormalities, meaning no masses, calcifications or distortions are found and the breasts are symmetrical (same size and shape).

Category 2: Benign (noncancerous) finding, meaning any abnormalities or changes found are noncancerous, including those from procedures such as biopsies that remove breast tissue.

Category 3: Probably benign, meaning there is no more than a 2% chance that any abnormalities found are cancerous. Follow-up imaging tests are typically recommended every six to 12 months until findings are considered stable.

Category 4: Suspicious abnormality, meaning one that is possibly cancerous, is found and a follow-up biopsy should be considered. This is divided into three groups:

• Category 4a, where there is a 2% to a 10% likelihood the abnormality is cancer
• Category 4b, where the likelihood that the abnormality is cancer ranges from 10% to 50%
• Category 4c, where there is a 50% to a 95% chance the abnormality is cancer

Category 5: Highly suggestive of malignancy, meaning there is a high chance (greater than 95%) that the abnormality is cancer, and a follow-up biopsy is strongly recommended.

Category 6: Known biopsy-proven malignancy, meaning it has already been determined by a breast biopsy that cancer is present (the mammogram is typically done to track how well the cancer is responding to treatment).

The radiologist will share the results with the patient’s doctor, typically within about 10 days of the imaging test. The patient will also receive an easy-to-read summary of the mammogram results within about 30 days.

The patient may meet with the doctor after the results are in to:

• Review the results
• Discuss a follow-up mammogram schedule
• Schedule a biopsy in cases where that is recommended

For abnormalities that may be malignant, women may be referred to a breast specialist for breast cancer diagnosis and treatment.

A full range of imaging services for women are offered at City of Hope^®, including screening, diagnostic and digital 3D mammograms. For patients diagnosed with breast cancer, our Breast Cancer Centers bring together compassionate experts in breast cancer treatment who have years of advanced training to help ensure each patient is provided with an optimized treatment care plan.