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Mammogram Memos: What You Need To Know

Medically reviewed by Carmen Fookes, BPharm. Last updated on July 11, 2022.

What Are Mammograms?

Mammograms are low-dose x-rays that are used to screen for breast cancer. A mammogram can pick up changes in breast tissue that cannot be felt, such as calcifications, cysts, fibroadenomas, and masses. A mammogram can also show how dense your breasts are. Screening mammograms are used in women who have no symptoms and who do not appear to have breast problems. An X-ray picture of each breast is usually taken from 2 different angles.

Mammograms can also be used to diagnose or detect breast disease in women with symptoms such as a lump or lumps, pain, skin dimpling, or nipple discharge. A diagnostic mammogram is used to get more information about breast changes and typically includes extra images of the breast that aren't routinely part of a screening mammogram.

How Safe Are Mammograms?

Mammograms use two plates to compress and flatten the breasts to spread the tissue apart. This allows for a better picture and also means a lower dose of radiation can be used.

On average, the total radiation dose for a mammogram that takes two images of each breast is about 0.4 mSv (a millisievert is a scientific unit of measurement for a radiation dose).

To put this into perspective, on average, most people in the U.S. are exposed to 3 mSV of radiation a year just from their natural surroundings. Those living at higher altitudes receive about 1.5 mSv more per year than those living near sea level. By far the biggest source of background radiation is radon in our homes (exposing us to an estimated 2 mSV per year).

Experts consider the benefits of mammography outweigh any possible harm from the radiation exposure, although if there is any chance you might be pregnant, let your health care provider and x-ray technologist know. Screening mammograms aren’t routinely done in pregnant women despite the risk to the fetus being very small.

What Happens During A Mammogram

You will be taken to a private area and asked to undress above the waist. The facility will give you a gown that opens at the front or a wrap to wear.

One breast is x-rayed at a time. A technologist will position your breast on the lower plate of the machine and then lower the plastic upper plate to compress your breast for just a few seconds while the technologist takes a picture. Slight pain or discomfort is normal during this stage of the procedure, although you should let the technologist know if it is unbearable. Two views of each breast are taken although more may be required for women with breast implants, large breasts, or with a diagnostic mammogram. The whole procedure usually takes about 20 minutes.

Scheduling In A Mammogram

There is some controversy about when women without any risk factors for breast cancer should start having mammograms.

The American Cancer Society recommends all women start having yearly mammograms at age 45, then have the option to switch to biennial (every two years) mammograms at age 55, and continue for as long as they are in good health and are expected to live for at least 10 years. Some women may choose to start having yearly mammograms from age 40.

These guidelines are for women at average risk for breast cancer which includes women that do not have a personal history of breast cancer, a strong family history of breast cancer, or a genetic mutation known to increase risk of breast cancer (such as in a BRCA gene), and who have not had chest radiation therapy before the age of 30.

The U.S. Preventive Services Task Force (USPSTF) recommend biennial screening for women aged 50 to 74 years. Some women may choose to start biennial screening earlier (between the ages of 40 and 49); however, the task force reported that evidence was insufficient to assess the benefits and harms of screening in women aged 75 or older.

These guidelines ONLY apply to asymptomatic women aged 40 or older without preexisting breast cancer or a previously diagnosed high-risk breast lesion. They do not apply to women who are at high risk for breast cancer because of an underlying genetic mutation (such as a BRCA1 or BRCA2) or a strong family history of breast cancer, a history of chest radiation at a young age, or with worrying symptoms. These women should get mammograms or undergo other imaging procedures at a frequency agreed upon with their doctor.

How To Prepare For Your Mammogram

If you have never had a mammogram before, choose a facility that specializes in mammograms and does many a day. Try to go to that facility every time you have a mammogram, so that a new mammogram can easily be compared to the one before. If you have changed where you get your mammograms done, try to get your old records from your previous facility (or have them sent to the new facility); this makes the odds of a false-positive finding less likely. In addition, tell your new facility about any biopsies or other breast treatments you have had done before.

If your breasts tend to get swollen or tender at certain times of the month, schedule your appointment for outside of those times. Avoid wearing deodorant on the day of the exam (it may show up as white spots), and consider wearing a skirt or pants so that only your top and bra will need removing for the mammogram.

And try not to worry. Only 2 to 4 screening mammograms out of 1,000 lead to a diagnosis of breast cancer.

When Will I Get The Results?

Before you have your mammogram, find out what the procedure is for getting the results back to you.

Some testing centers may give you the results on the spot. Others may prefer to send a detailed report to your doctor, who will let you know the findings in person. Whatever the policy is, make sure you know when to expect your results. Doctor's offices are busy places, and you should not assume that just because you haven't heard back from them after ten days that everything is normal. Mammography clinics must also mail you an easy-to-understand summary of your results, as quickly as possible (within 30 days), if the results suggest cancer is possible.

Mammograms can’t prove that an abnormal area is cancer. But they can help determine if further testing (such as an ultrasound, MRI, or biopsy) is needed.

What Could Show Up?

Doctors who read mammograms look for changes in your breast or spots, masses, or other suspicious areas that could be a sign of cancer. Having old mammograms available for the doctor to look at can help show that a certain spot or mass has not changed for years and is unlikely to be cancer.

The most common changes found by mammography are calcifications and masses. Mammograms also give an indication of breast density.

Calcifications are tiny calcium deposits within breast tissue that show up on a mammogram as small white spots. They may or may not be caused by cancer. Macrocalcifications (larger areas of calcium deposits) are usually related to noncancerous changes such as aging, injury, or inflammation and affect 50% of women over the age of 50. Microcalcifications (tiny specks of calcium) have a higher risk of being cancer, particularly if they have a suspicious look and pattern. A biopsy is the only way to tell if a calcification is cancerous.

Masses: Cancerous And Noncancerous Causes

A mass is another important change that may be seen on mammogram. They are areas of tissue that look abnormal and commonly turn out to be cysts or fibroadenomas. However, they can be cancer.

Cysts are fluid-filled sacs that are hardly ever cancerous, although they may feel the same as a tumor and look the same on a mammogram. An ultrasound may be performed (these are a better tool to see fluid-filled sacs), or a thin needle may be used to aspirate (remove) fluid from the area to rule out cancer.

Further imaging tests may be ordered if a cyst is partially solid or if doctors are not 100% certain it is a cyst. Sometimes, a biopsy (a small incision is made and a sample of tissue taken) is needed. Othertimes, the decision may be made to just perform regular mammograms and monitor the area for any changes. When making a decision about how likely the mass is cancer, doctors will take into account its size, shape, and margins.

Fibroadenomas: Common, Noncancerous Lumps

Fibroadenomas are lumps of glandular breast tissue and connective (stromal) tissue that are non-cancerous (also called benign).

They can occur at any age but simple fibroadenomas - where the tissue is the same throughout - tend to be more common in women in their 20s and 30s. Some are large enough to be felt and others will only show up on imaging tests, such as a mammogram. They are usually round with a distinct border, able to be moved under the skin, and firm, but not tender. A biopsy is the only sure way to confirm that the lump is a fibroadenoma, and not cancerous.

Some doctors may elect to remove fibroadenomas, particularly ones that keep growing; however, others may adopt a wait-and-see approach. Some fibroadenomas stop growing or shrink on their own as a woman gets older.

Simple fibroadenomas increase a woman's chance of breast cancer by about 1½ times.

What Are Dense Breasts?

Dense breasts are those that contain a lot of fibrous and glandular tissue, and not much fat in the breast. Dense breasts are very common and don't look or feel any different to less dense breasts. Breast density is not related to breast size or firmness and can only be seen on mammograms.

Research has found that dense breasts are associated with an increased risk of breast cancer. How much that risk is increased is controversial, but most studies have found an odds ratio of 4 or higher - meaning that women with dense breasts are four times more likely to develop breast cancer than other women.

Doctors assign breast density into one of four categories: from almost entirely fatty breasts to extremely dense breasts, which lowers the sensitivity of mammography.

Having dense breasts lowers the accuracy of mammograms because dense breast tissue, breast masses, and tumors all look white on a mammogram. This can make it harder to detect abnormal areas of tissue; however, it is still important to get regular mammograms.

Getting Called Back

So your doctor has been in contact and has requested you come back for another mammogram or a different imaging test such as an ultrasound or MRI. Should you panic?

No. Getting a call back after a screening mammogram is reasonably common, particularly if you have never had a mammogram before or your past results are unavailable. A call back does not mean you have cancer. Reasons include:

  • Dense breasts
  • Unclear pictures or areas of breast tissue missed or not showing up
  • Findings of a cyst, calcifications, or a mass
  • The mammogram has found an area of tissue that just looks different from normal breast tissue.

A repeat mammogram is called a diagnostic mammogram and will concentrate on any areas of concern. Sometimes an ultrasound or MRI will be used instead of a mammogram or in addition to a mammogram.

Try not to worry. Most repeat mammograms do not find cancer and in fact, less than 10% of women called back are diagnosed with breast cancer.

Downsides Of Mammography

Although mammograms are the best breast cancer screening tool we have at this time, they are far from perfect.

One problem with mammograms is the high number of false-positive results - this is when the mammogram looks abnormal, but there is no cancer in the breast. Extra testing (diagnostic mammograms, ultrasound, MRIs, biopsy) is usually required to rule out cancer. Almost 50% of women getting annual mammograms over a 10-year period will have a false-positive finding.

Mammogram results can also be falsely-negative. This is when the mammogram looks normal even though breast cancer is present. Approximately one in five breast cancers are missed by screening mammograms. Women with dense breasts have more false-negative results.

In addition, it is possible that some types of breast cancer found on mammogram would never grow or spread. Because doctors currently cannot predict which cancers would be life-threatening and which ones wouldn't, the majority are treated anyway. This is called over-diagnosis and over-treatment and these cancers never would have been found or treated if the woman had not gotten a mammogram. Up to 10% of cancers may be over-diagnosed.

For women with serious or life-threatening illnesses, such as heart failure, kidney disease, or chronic obstructive pulmonary disease (COPD), screening mammograms may not help extend your life expectancy. Discuss their value with your doctor.

What To Do If You Are Diagnosed With Cancer

It can be overwhelming finding out that you have cancer.

Your doctor may have told you the type and stage of your cancer already, and what treatment to expect, but when you are first given the news, it can be difficult to take it all in.

If you have been referred to a breast cancer specialist, make a list of questions to ask about your cancer (call the American Cancer Society at 1-800-227-2345 for advice). Take a friend or family member into the appointment with you to act as a second pair of ears and to help you remember things later. You may also like to record the conversation. Take notes and ask your doctor to explain anything you are not clear about.

Finding out more about your cancer gives you more control and is likely to reduce worry about the future.

Finished: Mammogram Memos: What You Need To Know

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  • Breast Cancer: Screening Jan 11, 2016. US Preventive Services Taskforce.,aged%2050%20to%2074%20years.&text=The%20decision%20to%20start%20screening,should%20be%20an%20individual%20one
  • American Cancer Society Recommendations for the Early Detection of Breast Cancer. American Cancer Society. 2022
  • What Is Breast Cancer Screening? Centers for Disease Control and Prevention. 2022.

Further information

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