Ask the Doctors

Dear Doctor: After a mammogram, I was told I have dense breast tissue and that instead of a regular mammogram, I need to start getting a 3D mammogram. Why would that be? What exactly is dense breast tissue, anyway?

Dear Reader: A woman’s breasts are made up of several different types of tissues. There are glandular tissues, which produce, store and deliver milk; connective tissues, which support the breast and help give it shape; and fatty tissues, which make up the rest of the breast. Fatty tissues help protect and support the glandular tissues, and they play a role in breast size. Breasts have no muscles, but they do also contain blood vessels, lymph vessels and lymph nodes.

Dense breast tissue is indicated when your mammogram reveals a high proportion of connective and glandular tissue, and a lower amount of fatty tissue. Up to half of all women are considered to have dense breast tissue. Unlike fatty tissue, which appears as dark and transparent on a mammogram, dense tissue reads as solid white. So do the tumors that mammograms are used to identify. As a result, the presence of a high proportion of dense breast tissue can make it easier for cancers and other potential problems to go undetected.

Like regular mammograms, the 3D mammogram is an image of the breast obtained using low-dose X-rays. The procedure for the 3D mammogram is also the same. You stand in front of the imaging machine, and your breast is compressed between two plates (yes, ouch) to flatten the tissue and to prevent movement while the X-ray is being taken. Both types of mammogram are used to identify early signs of breast cancer.

The 3D mammogram is different because, as the name suggests, it creates a multi-dimensional picture of the breast. This is achieved by capturing many images of the breast tissue from different angles, which generates thin cross sections of breast tissue. These combine to create a clearer and more detailed picture of the breast. The 3D mammogram, also known as breast tomosynthesis, takes a bit longer to complete than the standard mammogram. It emits a similar amount of low-dose radiation to the standard mammogram, but since it’s often used in addition to a standard mammogram, the total dose of radiation is higher.

For some women with dense breast tissue, even a 3D mammogram may not offer adequate diagnostic information. In these cases, the use of magnetic resonance imaging (MRI) or an ultrasound may be required. Other types of imaging tests are also being studied. These include an optical imaging test, which analyzes the movement of light through breast tissue, and molecular breast imaging, or MBI, which uses a radioactive tracer to identify the presence of cancer cells. Electrical impedance imaging distinguishes normal tissue from cancer cells through the use of a very small electrical current. None of these tests has yet been approved for breast cancer screening.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

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