A breast ultrasound is a non-invasive medical imaging technique that uses high-frequency sound waves to create real-time pictures of the tissues inside the breast. This procedure is not used for routine cancer screening but serves as a crucial diagnostic tool. Its primary function is to investigate a specific area of concern, such as a palpable lump or an abnormality identified on a prior mammogram. The resulting images help healthcare providers determine the nature of a finding, guiding the next steps in a patient’s care plan.
How Breast Ultrasound Complements Mammography
While mammography remains the standard for initial breast cancer screening, breast ultrasound provides supplementary information necessary for a complete diagnosis. Ultrasound excels at differentiating between a solid mass and a fluid-filled cyst, which appear indistinguishable on a mammogram. This ability to characterize internal structure is a major advantage.
Ultrasound is particularly useful for individuals who have dense breast tissue, which appears white on a mammogram and can obscure small tumors. An ultrasound can detect additional cancers not visible on the X-ray image because it does not rely on X-rays. It is frequently employed as a targeted examination to look at a suspicious spot or as a supplemental screening tool for patients with high breast density.
What to Expect During the Procedure
The breast ultrasound procedure is typically quick and involves minimal preparation. The patient lies comfortably on an examination table, often with an arm raised above the head. A sonographer or radiologist applies a small amount of warm, water-based gel onto the skin of the breast to facilitate the transmission of sound waves.
A handheld device called a transducer is gently pressed against the skin and moved across the area being examined. The transducer emits sound waves and captures the returning echoes to form the image on a monitor. The entire process is painless and generally takes about 10 to 20 minutes. Once the images have been captured, the gel is wiped off, and the patient is free to leave.
Key Visual Indicators of Malignancy
Radiologists analyze several visual characteristics of a mass on an ultrasound image to assess its potential for malignancy. The shape and orientation of the lesion are among the first features evaluated. A mass oriented vertically, often described as “taller-than-wide,” is considered suspicious because it suggests growth across tissue planes.
The appearance of the mass’s borders, or margins, is another important indicator. Benign masses usually have smooth, well-defined, and rounded margins, while cancerous masses often display irregular, angular, or spiculated margins. Spiculated refers to jagged, finger-like projections extending from the mass into the surrounding tissue, which is a strong visual clue of an invasive process.
Acoustic properties relate to how the sound waves interact with the tissue. Many malignant lesions are hypoechoic, meaning they appear darker than the surrounding tissue because they do not reflect sound waves well. A suspicious mass may also cause posterior acoustic shadowing, where the area immediately behind the lesion appears dark because the dense mass has absorbed the sound waves.
The evaluation often includes a Doppler study to assess the blood flow, or vascularity, within and around the mass. Increased blood flow suggests rapid growth and raises the suspicion for malignancy. These combined visual cues help the radiologist determine the likelihood of the mass being cancerous.
Interpreting the Standardized Results
The visual findings are translated into a standardized risk assessment using the Breast Imaging Reporting and Data System (BI-RADS), developed by the American College of Radiology (ACR). This system assigns a category number from 0 to 6, providing a clear recommendation for patient management. The final BI-RADS category is the most important part of the ultrasound report for the referring physician.
A finding assigned BI-RADS Category 3 is considered “probably benign” with a malignancy risk of less than two percent. Lesions in this category typically require a short-interval follow-up ultrasound, often in six months, to confirm stability rather than an immediate biopsy. This category is reserved for lesions with a distinctly benign appearance that warrant a cautious approach.
Findings with more suspicious features are classified as BI-RADS Category 4, which indicates a “suspicious abnormality” with a malignancy probability ranging from two to 95 percent, necessitating a biopsy. This wide range is often broken down into subcategories: 4A (low suspicion), 4B (moderate suspicion), and 4C (high suspicion), to better communicate the level of concern.
The highest level of concern is BI-RADS Category 5, which is “highly suggestive of malignancy.” This category is assigned to findings with classic cancer characteristics, such as a spiculated mass with posterior shadowing, and carries a greater than 95 percent probability of cancer. A finding in this category almost always leads to a tissue biopsy for a definitive diagnosis.