Breast Cancer Early Detection

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A mammogram is an x-ray of the breast. A diagnostic mammogram is used to diagnose breast disease in women who have breast symptoms or an abnormal result on a screening mammogram. Screening mammograms are used to look for breast disease in women who are asymptomatic; that is, those who appear to have no breast problems. Standard screening mammograms take 2 views (x-ray pictures taken from different angles) of each breast, while diagnostic mammograms may take more views of the breast. Women who are breastfeeding can still get mammograms, although these are probably not quite as accurate because the breast tissue tends to be dense.

For some women, such as those with breast implants, additional pictures may be needed to include as much breast tissue as possible. Breast implants make it harder to see breast tissue on standard mammograms, but additional x-ray pictures with implant displacement and compression views can be used to more completely examine the breast tissue. If you have implants, it is important that you have your mammograms done by someone skilled in the techniques used for women with implants.

Strict guidelines ensure that mammogram equipment is safe and uses the lowest dose of radiation possible. Many people are concerned about the exposure to x-rays, but the level of radiation used in modern mammograms is not thought to significantly increase the risk for breast cancer.

Modern mammogram equipment uses very low levels of radiation, on average a total dose of about 0.4 mSv for a typical mammogram with 2 views of both breasts (a mSv is a measure of radiation dose).

To put dose into perspective, people in the US are normally exposed to an average of about 3 mSv of radiation each year just from their natural surroundings (this is called background radiation). This means that the dose from a mammogram is the same as about 7 weeks of background radiation.

For a mammogram, the breast is compressed between 2 plates for a few seconds to flatten and spread the tissue. This may be uncomfortable for a moment, but it is necessary to produce a good, readable mammogram.

The procedure produces a black and white image of the breast tissue either on a large sheet of film or as a digital computer image that is “read,” or interpreted, by a radiologist (a doctor trained to interpret images from x-rays, ultrasound, magnetic resonance imaging, and related tests.) If the image is recorded on the computer instead of on film, it is called a digital mammogram (also known as a full-field digital mammogram or FFDM). This is available at most centers.

Breast tomosynthesis (3-D mammography)

This technology is basically an extension of a digital mammogram. For this test, the breast is compressed once and a machine takes many low-dose x-ray images as it moves over the breast. The images are recorded on a computer, which can be combine them into a 3-dimensional picture. 3-D mammography uses more radiation than most standard 2-view mammograms, but it may let doctors see problem areas more clearly. This might lower the chance that you will need to be called back for another mammogram right away. It may also be able to find more cancers. Breast tomosynthesis is not widely available, and its role in screening and diagnosing breast cancer is still not clear.

What the doctor looks for on your mammogram

The doctor reading your mammogram will look for several types of changes:

Calcifications are tiny calcium 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 2 types of calcifications, macrocalcifications which are coarse (larger) and are linked with benign (non-cancerous) conditions, and microcalcifications which are smaller and can sometimes mean that cancer is present. If microcalcifications look suspicious for cancer based on their shape and layout, a biopsy will be recommended.

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), cancers, 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. Sometimes the fluid in the cyst is removed with a thin, hollow needle.
  • If a mass is not a simple cyst (that is, if it is at least partly solid), then you might 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 determine if cancer is likely to be present.

Having your previous 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 is probably a benign condition and a biopsy is not needed.

The radiologist will also assess your breast density. Breast density is based on how much of your breast is made up fatty tissue vs. how much is made up of fibrous and glandular tissue.

If your breast density is higher than average, the letter you get about your mammogram results may say that you have dense breasts. Dense breasts are very common and don’t mean that there is anything wrong. Almost half of women have dense breasts on a screening mammogram. Although dense breast tissue can make it harder to find cancers on a mammogram, at this time, experts do not agree what other tests, if any, should be done in addition to mammograms in women with dense breasts who are not high risk based on other factors.

Limitations of mammograms

A mammogram cannot prove that an abnormal area is cancer. To confirm whether cancer is present, a small amount of tissue must be removed and looked at under a microscope. This procedure is called a biopsy. For more information, see our document For Women Facing a Breast Biopsy.

You should also be aware that mammograms are done to find cancers that can’t be felt. If you have a breast lump, you should have it checked by your doctor, who may recommend a biopsy even if your mammogram result is normal.Mammograms are not perfect at finding breast cancer. They do not work as well in women with dense breasts, since dense breasts can hide a tumor. Dense breasts are more common in younger women, pregnant women, and women who are breastfeeding, but any woman can have dense breasts.

This can be a problem for younger women who need breast screening because they are at high risk for breast cancer (because of gene mutations, a strong family history of breast cancer, or other factors). This is one of the reasons that the American Cancer Society recommends MRI scans in addition to mammograms for screening in these women.

At this time, American Cancer Society guidelines do not contain recommendations for additional testing to screen women with dense breasts who aren’t at high risk of breast cancer based on other risk factors.

For more information about mammograms, see our document Mammograms and Other Breast Imaging Procedures.

Tips for having a mammogram

Here are some useful suggestions for making sure that you receive a quality mammogram:

  • If it is not posted in a place you can see it near the receptionist’s desk, ask to see the FDA certificate that is issued to all facilities that offer mammography. The FDA requires all facilities to meet high professional standards of safety and quality in order to be a provider of mammography services. A facility may not provide mammography without certification.
  • Use a facility that either specializes in mammography or does many mammograms a day.
  • If you are satisfied that the facility is of high quality, continue to go there on a regular basis so that your mammograms can be compared from year to year.
  • If you are going to a facility for the first time, bring a list of the places, dates of mammograms, biopsies, or other breast treatments you have had before.
  • If you have had mammograms at another facility, you should make every attempt to get those mammograms to bring with you to the new facility (or have them sent there) so that they can be compared to the new ones.
  • Try to schedule your mammogram at a time of the month when your breasts are not tender or swollen to help reduce discomfort and assure a good picture. Try to avoid the week right before your period.
  • On the day of the exam, don’t wear deodorant or antiperspirant. Some of these contain substances that can interfere with the reading of the mammogram by appearing on the x-ray film as white spots.
  • You may find it easier to wear a skirt or pants, so that you’ll only need to remove your blouse for the exam.
  • Always describe any breast symptoms or problems that you are having to the technologist who is doing the mammogram. Be prepared to describe any medical history that could affect your breast cancer risk − such as surgery, hormone use, or family or personal history of breast cancer. Also discuss any new findings or problems in your breasts with your doctor or nurse before having a mammogram.
  • If you do not hear from your doctor within 10 days, do not assume that your mammogram result was normal. Call your doctor or the facility.

What to expect when you get a screening mammogram

  • To have a mammogram you must undress above the waist. The facility will give you a wrap to wear.
  • A technologist will be there to position your breasts for the mammogram. Most technologists are women. You and the technologist are the only ones in the room during the mammogram.
  • To get a high-quality mammogram picture, it is necessary to flatten the breast slightly. The technologist places the breast on the mammogram machine’s lower plate, which is made of metal and has a drawer to hold the x-ray film or the camera to produce a digital image. The upper plate, made of plastic, is lowered to compress the breast for a few seconds while the picture is taken.
  • The whole procedure takes about 20 minutes. The actual breast compression only lasts a few seconds.
  • You may feel some discomfort when your breasts are compressed, and for some women compression can be painful. Try not to schedule a mammogram when your breasts are likely to be tender, as they may be just before or during your period.
  • Although usually 2 views of each breast are usually taken for a screening mammogram, for some women, such as those with breast implants, additional pictures may be needed.
  • All mammogram facilities are now required to send a copy of your results in simple language to you within 30 days. Generally, you will be contacted within 5 working days if there is a problem with the mammogram.
  • Being called back for more testing does not mean that you have cancer. In fact, less than 10% of women who are called back for more tests are found to have breast cancer. Being called back occurs fairly often, and it usually just means an additional image or an ultrasound needs to be done to look at an area more clearly. This is more common for first mammograms (or when there is no previous mammogram to look at) and in mammograms done in women before menopause. It may be slightly less common for digital mammograms.
  • Only 2 to 4 screening mammograms of every 1,000 lead to a diagnosis of cancer.

If you are a woman 40 or over, you should get a mammogram every year. You can schedule the next one while you’re there at the facility. Or, you can ask for a reminder to schedule it as the date gets closer.

For more information on mammograms and other imaging tests for early detection and diagnosis of breast diseases, see our document Mammograms and Other Breast Imaging Procedures.

Last Medical Review: 09/10/2014
Last Revised: 09/10/2014