Imaging tests for breast disease

Several types of imaging tests that may be used to look for or help evaluate breast diseases are described briefly here. For more detailed information about these and other imaging tests, please see our document, Mammograms and Other Breast Imaging Procedures.

Mammograms

A mammogram is an x-ray of the breast. Mammograms are mostly used for screening. Screening mammograms are used to look for breast cancer in women who have no breast symptoms.

Mammograms can also be used to look at a woman's breast if she has breast symptoms or an abnormal screening mammogram. When used in this way, they are called diagnostic mammograms. They can be used to find out more about a breast lump (mass), nipple discharge, or an area found on a screening mammogram that doesn't look normal. In some cases, special images known as cone views with magnification are used to "zoom in" on a small area of altered breast tissue to make it easier to evaluate.

Some imaging centers may offer digital mammography (also known as full-field digital mammography or FFDM). Whereas standard mammograms are recorded on large sheets of photographic film, digital mammograms are recorded as files on a computer. After the exam, the doctor can look at the pictures on a computer screen and adjust the image size, brightness, or contrast to see certain areas more clearly. Not all centers offer this, but it is becoming more widely available with time.

What the doctor looks for on your mammogram: The doctor reading the mammogram will look for several types of changes.

Calcifications are tiny mineral deposits within the breast tissue. They look like small white spots on the films. They may or may not be caused by cancer. There are 2 types of calcifications:

• Macrocalcifications are coarse (larger) calcium deposits that are most likely changes in the breasts caused by aging of the breast arteries, old injuries, or inflammation. These deposits are related to non-cancerous conditions and do not require a biopsy. About half of women over 50, and 1 in 10 women under 50 have macrocalcifications.
• Microcalcifications are tiny specks of calcium in the breast. They may be alone or in clusters. Microcalcifications seen on a mammogram are of more concern than macrocalcifications, but still do not usually mean that cancer is present. The shape and layout of microcalcifications help the doctor judge how likely it is that cancer is present. If the microcalcifications look suspicious, a biopsy will be needed.

Masses, which may or may not have calcifications, are another important change seen on mammograms. Masses can be many things, including cysts (non-cancerous, fluid-filled sacs) and non-cancerous solid tumors (such as fibroadenomas), but they could also be cancer.

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 solid tumor can feel the same on physical exam. They can also look the same on a mammogram. To confirm that a lump (mass) is really a cyst, a breast ultrasound is often done. The doctor may also remove (aspirate) the fluid from the cyst with a thin, hollow needle to have it checked for cancer cells.
• If a mass has any solid parts (that is, if it is not a simple cyst), you may need more imaging tests. Some masses can be watched over time with mammograms, while others may need to be biopsied. The size, shape, and margins (edges) of the mass can help the doctor figure out if cancer is present.

Having your older mammograms available to the doctor is very important. They can help to show that if a mass or calcification has stayed the same for many years. This would mean that it is probably a benign condition and you will not need a biopsy.

Mammograms have limitations: Diagnostic mammograms can be used to find out more about a breast lump (mass), nipple discharge, or an area found on a screening mammogram that doesn't look normal. But a mammogram by itself 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. A mammogram may show:

• That the abnormal area is not worrisome at all. In these cases the woman can usually return to having routine yearly screening mammograms.
• That the abnormal area is very likely to be benign (not cancer). In these cases, it is common to ask the woman to come back sooner than usual for her next mammogram, usually in 4 to 6 months.
• That the abnormal area is more suspicious, and a biopsy (removal of a small piece of the area) is needed to tell if it is cancer.

Even if the mammogram does not show a tumor, if you or your doctor can feel a lump, then usually a biopsy will be needed to make sure it isn't cancer. One exception would be if a breast ultrasound shows that the lump is a simple cyst (a fluid-filled sac).

Mammograms are not perfect at finding breast cancer. They do not work as well in younger women, because their breasts are often dense, which can hide a tumor. This may also be true for pregnant women and women who are breastfeeding. Since most breast cancers occur in older women, this is usually not a major concern. But this can be a problem for young women who are at high risk for breast cancer (due to gene mutations, a strong family history of breast cancer, or other factors) because they often develop breast cancer at a younger age.

If you have a breast lump, you should have it checked by your doctor and consider having it biopsied even if your mammogram is normal. A biopsy may be the only way to know for sure if a breast change is cancer.

Breast ultrasound

Ultrasound (US), also known as sonography, uses sound waves to look inside the body. A handheld instrument placed on the skin sends the sound waves through the breast. Echoes from the sound waves are picked up and translated by a computer into a black and white image on a computer screen. This test is painless and does not expose you to radiation.

Ultrasound is useful for evaluating some breast masses that are found on a mammogram or on a physical exam. It has become a valuable tool because it is widely available, non-invasive, and costs less than other options. This test helps distinguish between cysts (fluid-filled sacs) and solid masses and sometimes can help tell the difference between benign and cancerous tumors. Still, ultrasound cannot be used instead of mammograms for breast cancer screening.

Breast ultrasound may also be used to help doctors guide a biopsy needle into some breast lesions.

Magnetic resonance imaging (MRI) of the breast

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. A contrast material called gadolinium is often used so the doctor can see details better.

Patients have to lie inside a narrow tube for this test, face down on a platform specially designed for the procedure. The platform has openings for each breast that allow them to be imaged without compression. The platform contains the sensors needed to capture the MRI image. The tube is confining and can upset people with claustrophobia (a fear of enclosed spaces). The machine also makes loud buzzing and clicking noises that some people find disturbing. Some places provide headphones to block out the noise.

MRI machines are quite common, but they need to be specially made or adapted in order to look at the breast. It is also important that the MRI facility can also do a MRI guided biopsy if it is needed. That means that not every center with an MRI machine can do a breast MRI.

Breast MRI can be used along with mammography for screening some women who have a high risk of getting breast cancer. It can also be used to better look at suspicious areas seen on a mammogram, especially if ultrasound is not helpful. MRI can also be used to guide biopsies so that the doctor can be sure to get tissue from the area of concern.

Ductogram

This test, also called a galactogram, is sometimes helpful in finding the cause of bloody nipple discharge. In this test a very thin plastic tube is placed into the opening of the duct at the nipple that the discharge is coming from. A small amount of contrast medium ("dye") is injected, which outlines the shape of the duct on an x-ray image. The x-ray can usually show if there is a tumor inside the duct.