How are mammogram findings in breast cancer interpreted?

Updated: Oct 17, 2016
  • Author: Nagwa Dongola, MD, FRCR; Chief Editor: Peter Eby, MD  more...
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Answer

The quality of the mammograms should be assessed, and if not optimal, repeat examinations may be ordered. Mammograms of the right and left breasts are displayed on a high resolution monitor with previous comparable projections. Lighting should be homogeneous, and adequate viewing conditions should be maintained. The mammograms are inspected carefully. The search is done systematically through similar areas in both breasts. The goal of the radiologist is to determine whether the findings are normal, benign, or suspicious enough to warrant tissue sampling.

First, breast symmetry, size, general density, and glandular distribution are observed. Next, a search for masses, densities, calcifications, architectural distortions, and associated findings is performed. For masses, the shape, margins, and density are analyzed. The features of benign and malignant masses can be similar. Benign masses are often round or oval with circumscribed margins. Malignant lesions tend to have irregular, indistinct, or spiculated margins. Malignancies tend to have density greater than that of the normal breast tissue. The presence of very low density fat in a lesion often indicates benign findings such as oil cysts, lipomas, galactoceles, and hamartomas.

Calcifications can also be the first sign of cancer or a harmless process in the breast. Benign calcifications are usually larger than calcifications associated with malignancy. They are usually coarser, often round with smooth margins, and more easily seen. Benign calcifications tend to have specific shapes: eggshell calcifications in cyst walls, tramlike in arterial walls, popcorn type in fibroadenomas, large and rodlike with possible branching in ectatic ducts, and small calcifications with a lucent center in the skin.

Calcifications associated with malignancy are usually small (< 0.5 mm) and often require high-resolution magnification imaging with digital zooming for accurate assessment. They tend to have a pleomorphic or heterogeneous shape or a fine granular, fine linear, or branching (casting) shape.

The distribution of the calcification can provide clues to the underlying process and should be specified as grouped, clustered, linear, segmental, regional, or diffuse.

Special findings may be encountered, such as a linear density that might represent a duct filled with secretions or a reniform-shaped mass with a radiolucent center that is typical of an intramammary lymph node.

Associated findings are then taken into account. These include skin or nipple retraction, skin thickening (which may be focal or diffuse), trabecular thickening, skin lesions, axillary adenopathy, and architectural distortion.

Diagnostic views are used to determine where each lesion is in the breast. These may be described as central, retroareolar, in a quadrant, or, more precisely, at a clock position. The breast is viewed as the face of a clock with the patient facing the observer. The depth of the lesion is assigned to the anterior, middle, or posterior third of the breast.

If previous examination results are available, their comparison is useful in assessing disease progress.

All of these findings are considered together, a final impression is formed, and a BI-RADS category is assigned.


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