Mammography is an important tool for breast health, serving as a screening method to detect changes within breast tissue. Its purpose is to identify indicators of breast cancer at an early stage, when treatment options are more effective. Understanding mammography images can provide valuable insight.
What Mammography Images Show
Mammography uses low-dose X-rays to generate images of the breast’s internal structures, known as mammograms. These images appear in shades of black, gray, and white, with color indicating tissue density. Less dense fatty tissue appears darker or more transparent, while denser tissues, such as glandular and fibrous tissue, appear white.
Radiologists examine these images, looking for differences in tissue density, symmetry between the breasts, and areas of concern. A normal mammogram displays a largely gray background with some white areas representing healthy, dense tissue, and a consistent pattern across both breasts. Appearance can vary, making comparison to previous mammograms useful for detecting changes over time.
Understanding Breast Density
Breast density refers to the proportion of fibrous and glandular tissue compared to fatty tissue within the breast. This characteristic is determined by a mammogram and cannot be assessed by touch or breast size. On a mammogram, both dense breast tissue and abnormalities, such as tumors, appear white.
This similarity can make it challenging for radiologists to detect abnormalities in dense breasts, as they can be obscured by surrounding tissue. Breast density is categorized using a four-level system, from almost entirely fatty to extremely dense. Individuals with higher breast density, especially those with heterogeneously or extremely dense breasts, may have an elevated risk of breast cancer and may benefit from additional screening beyond mammography.
Common Findings on a Mammogram
Radiologists examine mammograms for patterns and findings that can indicate normal breast tissue or abnormalities. Healthy breast tissue is symmetrical and consistent, with fatty areas appearing dark and glandular or fibrous areas appearing white.
One common finding is calcifications, which are tiny calcium deposits that show up as small, bright white spots on a mammogram. These are classified into macrocalcifications and microcalcifications. Macrocalcifications are larger, often round or coarse, and are almost always benign, not requiring further investigation. Microcalcifications are much smaller, resembling fine white specks, and while often benign, certain patterns, such as tight clusters or linear arrangements, can be an early sign of precancerous cells or breast cancer, requiring further evaluation.
Masses appear as a lump or an area of abnormal tissue. These can be fluid-filled cysts, which are benign and appear as well-defined, dark structures with smooth walls on an ultrasound. Solid masses include benign fibroadenomas or suspicious tumors. Fibroadenomas are smooth, round or oval, mobile lumps composed of fibrous and glandular tissue, appearing as circumscribed masses on a mammogram.
Tumors, whether benign or cancerous, appear as focused white areas on a mammogram. Their shape, margins (edges), and density help distinguish them; irregular shapes or indistinct/spiculated margins are more concerning for malignancy.
Architectural distortion is a finding where normal breast tissue appears pulled or distorted without a clear mass. This disruption may manifest as thin lines radiating from a point or focal retraction of tissue. While benign conditions like surgical scars or radial scars can cause architectural distortion, it is a suspicious finding that warrants further investigation due to its association with malignancy.
Interpreting Your Results and Next Steps
Mammogram results are communicated using the Breast Imaging-Reporting and Data System (BI-RADS), a standardized scoring system. This system assigns a category from 0 to 6 to describe findings and recommend next steps. Understanding these categories helps patients understand their report and necessary actions.
A BI-RADS Category 0 indicates an incomplete assessment, meaning more imaging (e.g., additional views or an ultrasound) or comparison with prior mammograms is needed for a definitive assessment. Category 1 signifies a negative result, indicating no abnormal findings, and routine annual screening is recommended. Category 2 means the findings are benign, but a specific non-cancerous finding (e.g., a cyst or benign calcification) is noted for future reference.
For a BI-RADS Category 3, the finding is probably benign (less than 2% chance of cancer). In these cases, a short-term follow-up mammogram, in six months, is advised to monitor for any changes. Category 4 signifies a suspicious abnormality that may be cancerous, with the likelihood ranging from 2% to 95%, and requires a biopsy for diagnosis.
Category 5 indicates findings highly suggestive of malignancy (greater than 95% chance of cancer), and a biopsy is strongly recommended. Category 6 is used when a biopsy has confirmed malignancy, guiding treatment and ongoing imaging. Most abnormal findings on mammograms ultimately prove to be benign.