Because small breast cancers are difficult to distinguish from normal tissue on a mammogram and may not be palpable during a breast exam, some go undetected. Cases that elude diagnosis are referred to as false negatives. These cancers are usually found after they have grown to a size that can be seen or felt.
Other conditions in the breasts may look similar to cancer, such as calcifications or cysts. Usually, the radiologist will ask for additional studies that focus on the area of the breast where the suspicious lesion is located. If additional studies are inconclusive, a biopsy is recommended. If the biopsy proves to be noncancerous, the finding is called a false positive.
Calcifications commonly develop in women's breasts because the breasts produce milk, which contains calcium. Because many breast cancers contain calcifications, it is important to determine whether or not calcifications are within cancerous tissue. Most calcifications can be evaluated a mammogram. Those that are difficult to evaluate require additional studies.
A mass, or lump, found on a mammogram may be a lymph node, cyst, or fibroadenoma (fibrous milk gland). These types of masses usually are easy to identify and do not require additional studies. A new mass or a mass that has grown since the last mammogram was taken is usually evaluated with ultrasound.
Several masses can be seen in women who have fibrocystic disease. If there has been a change in the size or the shape of the edges of a mass, or if a suspicious calcification within a mass is seen, the radiologist may order additional studies.
An area in one breast that has a distinctly different appearance than the same area in the other breast is referred to as asymmetric density. This finding usually requires additional studies with mammography or ultrasound.
Dense breast tissue can make mammogram evaluation difficult because the tissue can obscure small cancers.
Diagnostic Mammography Imaging
Diagnostic imaging is required under certain circumstances:
- Breast implants
- Severe fibrocystic disease
- After surgery for early breast cancer that did not remove the entire breast
- Abnormal finding on a screening mammogram (e.g., change in a mass)
- New finding during clinical breast examination (e.g., lump, nipple discharge)
Types of imaging used for diagnosis include special mammographic views, mammographic views taken from different angles, and ultrasound. If the findings obtained from additional studies indicate that there is a solid lesion, a biopsy is recommended.
Special mammographic views include magnification and spot compression. Magnification produces an enlarged image of a portion of the breast that contains small calcifications or small masses. Spot compression applies more pressure to a small region in the breast. This thins out an area of dense tissue so that the x-rays produce a clearer image, making it easier for the radiologist to see if the tissue is normal or abnormal.
Sometimes views of the breast from different angles are required to see a questionable area. Typical additional views include:
- Cleavage viewBoth breasts are compressed between a set of panels at the same time and a top-to-bottom view of a suspicious finding in tissue between the breasts.
- Rolled viewThe breast is rolled to the right or left, compressed, and a top-to-bottom view is taken of a questionable area located in dense tissue.
- Mediolateral viewThe view is taken from the center of the chest to the outer side of the breast.
- Lateromedial viewThe view is taken from the outer side of the breast to the center of the chest.
Ultrasound is used to determine if a mass is a cyst or a possible cancer. Ultrasound is performed with a small, handheld device called a transducer. First, a gel is spread on the skin of the breast. The radiologist passes the transducer over the breast, which directs sound waves through the skin into the body. The sound waves create an image of the breast on a computer monitor.