Elastography and How It Helps Diagnose Breast Cancer

What is elastography and what role may it play in breast cancer screening?

Before you can treat breast cancer, you've got to find it. Detecting breast cancers early can save lives and reduce the disfigurement and illness that often accompany treatment.

What Is Elastography?

So, for many decades, researchers have tried to find better ways to detect breast cancer. In 1980, about four out of every five women who contracted breast cancer found the lump on their own. Although breast self-examination is still important, most breast cancers today are discovered when a woman has a mammogram, ultrasound or MRI (magnetic resonance imaging).

Breast Biopsy and Benign Lumps

But even when a test reveals a suspicious lump, the only accepted way today to find out for sure whether it is cancerous is to do a breast biopsy. Ultrasound and MRI imaging can detect small cancers in some women better than a mammogram, but they also show benign as well as malignant lesions.

This is one reason that about four out of every five breast biopsies shows that the suspected area was benign In other words, 80% of biopsies are needed only to rule out cancer.
The surgery involved with biopsies is costly and involves its own risks. So, for many years, women and their doctors have hoped for a diagnostic test that would both detect suspicious areas inside a breast and tell whether or not it is cancerous, without invasive surgery. After more than two decades of research, a promising new technique called elastography may be ready to fulfill that hope.

Elastography - How Does It Work?

Elastography combines the latest in ultrasonic imaging technology with the oldest form of breast cancer detection: touch. When a woman or her doctor presses on breast tissue to feel for unusual lumps, she touches the breast with a small amount of force. This force causes the breast structure to move in a characteristic way. The technical term for the way a solid moves in response to a force is called elasticity. If you have ever felt a breast with a cancerous tumor above a certain size, you know that the tumor usually feels like a hard, inflexible lump, almost like a rock or a peach pit. Scientists say that cancerous tumors have very low elasticity - they do not change shape readily when pressed. It is this property that enables elastography to work.

Kitchen Science Demonstration - How Does Elastography Work?

To explain how elastography works, we went into the kitchen and made a four-layer Jell-O ® mold - orange, lime, lemon, and strawberry flavors, all with different colors. We put an almond between the lemon and strawberry layers to represent a hard object such as a tumor.

Check the next slide to see what happens.

Elastography Demonstration Continued

When we took the gelatin out of the mold and set it on a plate, the layers made nice straight flat lines:

The almond doesn't change shape (if it looks like it does, that's because of optical distortion through the gelatin). But the more flexible (elastic) gelatin bends under pressure because it is more elastic than the almond.

How Is an Elastogram Done?

To take an "elastogram" of a breast, first a sophisticated ultrasound machine images the breast. Normal breast tissue has small features that show up in ultrasound images, and these features work as position markers for what comes next. If there are any lumps, these will show up too, but so far the ultrasound image does not tell the doctor anything more than the fact that there are suspicious lumps, which mammograms do as well.
The critical step comes next. A small amount of controlled pressure is applied to the breast, just enough to move it slightly. (This pressure is probably much less than you receive when your breasts are squeezed to take a conventional mammogram.) With the pressure applied (think "spoon on top of gelatin"), the system takes another ultrasound image. Then, a computer program compares the two images and produces a map showing how elastic the different regions are. This map, called an elastogram, is very effective in revealing hard, inflexible lumps, which are almost always cancerous.

The more flexible lumps are typically benign.

Elastography - Results and the Future of Breast Cancer Diagnosis

Researchers at several institutions in Europe and the United States have developed elastography techniques for breast cancer and other purposes since the early 1990s. The 2 primary techniques are referred to as compression-based elastography (or free-hand) and shear wave elastography.

In several studies, these techniques have been able to tell when a tumor would be benign on biopsy around 90% of the time. There have been few false positives (when a benign tumor looks malignant) and false negatives (when a tumor appear benign and is actually cancerous). There is some concern that "soft" breast cancers such as mucinous carcinoma would cause false negatives, and "hard" benign breast tumors such as fibrous adenomas would cause false positives, and these thoughts are still being considered.

Overall, studies to date appear very promising, with a recent review of the literature concluding that use of elastography may help guide the process of distinguishing benign and malignant breast lumps in the future.

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