Mammography is an X-ray examination that is essential for the early detection of breast cancer. But it can also detect benign changes in the breast. Find out how mammography works, how it is performed and what the benefits and risks are. Plus: All the facts about mammography screening in Switzerland and the incidence of breast cancer.

Overview: What is a mammogram?

Mammography is an X-ray examination of the breast that allows us to detect benign and malignant changes. These include, for example, fibroadenomas, lipomas, mastopathy, microcalcifications as an indication of breast cancer precursors or breast cancer (breast carcinoma) itself. Cysts, which also occur in the breasts of many women, are easier to detect with breast cancer ultrasound (sonography).

In conventional mammography, the breasts are pressed firmly together one after the other between two Plexiglas plates. Medical-technical radiology assistants (MTRA) then take images of each breast from two different directions. The result is a total of four X-ray images in black and white – two of each breast. We then interpret these and classify the findings as normal or suspicious.

Breast CT device

We often combine mammography with other imaging procedures, such as breast ultrasound (breast ultrasonography) or magnetic resonance imaging (breast MRI). In suspected cases, they provide further information, which we put together like pieces of a puzzle and then come to an assessment.

When is mammography used?

Mammography can provide important diagnostic information in various cases. Examples are:

  • Early detection of breast cancer – this is considered the most important method for detecting breast cancer in good time.
  • Familial risk of breast cancer – breast cancer occurs more frequently in some families and close relatives have an increased risk of also developing the disease.
  • Clarification of abnormalities, such as a lump or hardening in the breast
  • Mammography screening: A serial examination of healthy women without symptoms of breast cancer (from the age of 50, every two years, in some cantons in Switzerland) – mammography is carried out according to precisely defined quality criteria.
  • Follow-up care for women who have already had breast cancer – a possible relapse can be detected.

How does a mammogram work?

Mammography is a quick and uncomplicated examination of the breast in which we use X-rays to “x-ray” the breast in several planes. An X-ray tube integrated into the device generates the X-rays. In most cases, we now use digital mammography. This means that the images can be analyzed, stored and archived electronically. This means that we can always make “before and after comparisons” at the next mammogram. Today, only a few radiology practices still use analog mammography with film plates.

We take images of both breasts in two planes: The X-rays penetrate the breasts once from top to bottom and again from the oblique side. “Craniocaudal” and “mediolateral oblique” are the technical terms for the different directions. We then receive four mammography images.

What do you see on the mammogram images?

On these black and white images – the mammograms – we can detect abnormalities in the breast, for example lumps or hardenings that have previously been palpated or are visible on the ultrasound image. Mammography also reveals changes in the glandular, connective and fatty tissue of the breast that cannot be seen or felt from the outside. One example is microcalcifications. They form when cells die and the breast tissue remodels. This fine microcalcification is an important indicator of precancerous breast lesions or even breast cancer itself.

There are various benign as well as malignant changes in breast tissue. Benign tumors usually appear uniformly dense and have a smooth border on the outside. Malignant tumors, on the other hand, often do not have a sharp border, but “fray”. We can also see the size of the change on a mammogram. As a rule, two radiologists assess the images independently of each other. Because the principle applies: “Four eyes see more than two.”

However, mammography images do not allow us to say with certainty whether a woman actually has breast cancer or not. This is because the informative value of mammography depends on various factors, such as the density of the glandular tissue or age. In younger women under the age of 40, the breast tissue is usually very dense, which makes diagnosis more difficult. In case of doubt, only a tissue sample, the biopsy, can provide certainty. We take cell material from the suspicious area. A pathologist then analyzes it under a microscope in the laboratory. Benign and malignant cells can be distinguished with a high degree of certainty.

Radiation exposure due to mammography

Like any X-ray examination, mammography is also associated with a certain amount of radiation exposure. However, the radiation dose is comparatively low. Experts classify the risk of X-rays altering the genetic material of cells and thus causing cancer as minimal. The benefits of the study are many times greater, she concludes. High quality and safety standards also apply when carrying out a mammogram so that no woman is exposed to an unnecessary risk due to high radiation exposure.

Mammography: The procedure step by step

You can have a mammogram performed in a radiology practice, in a certified breast center or at the University Hospital. It is important that you inform yourself well in advance about the opportunities and risks of a mammogram. There is a lot of information material available, but you can also ask us. Only then will you decide whether or not you want to have a mammogram. A few tips in advance:

  • If possible, do not use deodorant before the mammogram. Residues may remain on the skin, which may subsequently impair the image quality.
  • Choose clothes that you can remove quickly and easily. The mammography procedure can be described as follows: you uncover your upper body in the cabin and remove all jewelry, piercings and other movable metal parts.
  • In the room where the mammography machine is located, you will usually be alone with the specialist carrying out the examination.
  • Stand as loosely as possible in front of the device and allow the specialist to guide you into the correct position. Follow the instructions given to you by the staff as closely as possible – this is the quickest way.
  • The breast is now carefully placed in the correct position between two Plexiglas plates, pressed flat together and fixed in place. This makes the tissue more permeable to the X-rays, the necessary radiation dose is lower and the images are subsequently more informative. Some women find the compression painful. Talk to the specialist staff if it is too tight for you. As a rule, however, the pressure is well tolerated for the short time of the examination. Squeezing does not damage the breast.
  • Avoid unnecessary movements, otherwise the images will be blurred.
  • Four exposures from top to bottom and from diagonal to side mean changing position four times and compressing the breast four times. But normally the mammogram is over after a few minutes.

Ideal time for mammography

The best time for a mammogram is during or in the first week after menstruation. This is when the fluid content of the breast is at its lowest and the tissue is soft and elastic. We can judge the pictures best here. However, if you are concerned about a lump or change, you can have a mammogram at any time. After the last menstrual period – the menopause – the timing no longer plays a role.

Mammography screening in Switzerland - not in every canton

Some cantons in Switzerland offer mammography screening for women aged 50 and over. By this, experts mean a screening of healthy women who have no symptoms that would indicate breast cancer. They receive an invitation every two years. The examination is free of charge for women – health insurance companies pay for it. The screening must meet high, legally defined quality requirements and should be accessible to every woman of the appropriate age. At least two specialists must assess the mammography images independently of each other. In addition, the programs have special requirements for the training of the persons who perform and assess the mammography. However, mammography screening is not available in all Swiss cantons.

The offer for women exists, for example, in the cantons of Basel-Stadt, Bern, Fribourg, Geneva, Graubünden, Jura (incl. Bernese Jura), Neuchâtel, St. Gallen, Ticino, Thurgau, Vaud and Valais. The introduction is planned in some cantons. In cantons without a screening program, early detection takes place outside of it. Always discuss the possibilities of mammography with your doctor. Swiss Cancer Screening provides an overview of breast cancer screening options in the various cantons in Switzerland.

Mammography screening: advantages

Mammography screening has a number of advantages and disadvantages, which you should find out about beforehand. There is extensive information material available, but you can also consult your doctor. Only then do you decide whether you want to take part or not. The most important advantages and some figures:

  • A quality-assured mammography program can prevent deaths from breast cancer. This has been proven by scientific studies.
  • If 1,000 women over the age of 50 regularly take part in mammography screening every two years, 16 women will die from breast cancer in the following 20 years.
  • If these 1,000 women never took part in breast cancer screening, 20 women would die from breast cancer.
  • Over a period of 20 years, screening therefore saves four women from dying of breast cancer.
  • If we detect breast cancer early, the cancer treatment is less intensive and less stressful. In the early stages, breast cancer also has a very good chance of being cured.

Mammography screening: disadvantages

The main disadvantages of mammography screening are:

  • Mammography can lead to false-positive results. The change is classified as possible breast cancer, but ultimately turns out to be benign. In this case, women must undergo further examinations, such as a biopsy. This, in turn, is associated with risks. They are also unnecessarily frightened. An example calculation: out of 1,000 women aged 50 and over who regularly take part in mammography screening every two years, 250 women will receive an abnormal finding. In about 185 of these women, the change turns out to be benign after further examinations – these findings are therefore false-positive. Around 65 women are diagnosed with breast cancer.
  • Conversely, mammography can also provide false-negative results. The breast cancer is not visible on the pictures and we mistakenly give the all-clear. Nevertheless, the woman has breast cancer, which initially remains undetected. It can continue to grow and then requires more intensive treatment. The chances of recovery are also less favorable with more advanced breast cancer.
  • Mammography harbors the risk of overdiagnosis and overtreatment. We find smaller tumors in the breast that grow slowly and would probably not have become dangerous for the woman during her lifetime. The women then receive treatment that might have been unnecessary, such as surgery, chemotherapy or radiotherapy. However, we are usually unable to predict which tumors will remain harmless and which will not.
  • Sometimes we also find malignant tumors that are aggressive and no longer treatable or curable. This means a longer period of suffering for the women, but not a longer life.
  • A so-called “interval cancer” can develop. Breast cancer sometimes develops within the two years between mammography screenings.

The Swiss Cancer League recommends and supports the mammography screening program. In her view, it has far more advantages than disadvantages. All cantons should therefore develop and introduce such breast cancer screening programs. This is also important in terms of equal opportunities. The Swiss Medical Board – a Swiss body that assesses medical services – takes a different view. In a 2014 report, it concluded that existing mammography programs should be limited in time and that no new programs should be introduced.

Breast cancer in Switzerland - incidence and age

Breast cancer is the most common cancer in women, including in Switzerland. In Germany, around 6,000 women are newly diagnosed with breast cancer every year. Around 80 percent of women are aged 50 or older when they are diagnosed with breast cancer. Breast cancer is comparatively rare in young women. A malignant tumor in the breast is the most common cause of cancer-related death. More than 1,400 women die of breast cancer every year. Nevertheless, the chances of recovery are good compared to other types of cancer such as lung or pancreatic cancer. Around 80 percent of women are still alive five years after diagnosis. The earlier we find the breast cancer, the better and more gently it can be treated and the more favorable the prognosis.

About the clinical picture of breast cancer

For patients

For mammography, breast CT, breast ultrasound and 3D breast ultrasound, you can either register yourself or be referred by your family doctor or specialist.

Tel. +41 43 254 41 10

For referrer

University Hospital Zurich
Institute for Diagnostic and Interventional Radiology
Rämistrasse 100
8091 Zurich

Tel. +41 43 254 41 10
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