Medical ultrasound is a non-invasive imaging method that uses high-frequency sound waves to create real-time pictures of the internal structures of the breast. Unlike mammography, this diagnostic tool does not use radiation, making it a safe option for evaluating breast tissue. A specialized transducer sends sound waves into the body and then captures the echoes that bounce back from the tissue interfaces. These echoes are processed to form a detailed, moving image displayed on a monitor, which assists physicians in assessing breast health.
The Role of Ultrasound in Breast Health Diagnosis
Breast ultrasound is typically employed as a supplementary examination rather than a primary screening method for the general population. It is often performed after an abnormality, such as a palpable lump or an area of concern, is detected on a screening mammogram or felt during a clinical exam. This focused approach allows the radiologist to target a specific area for closer, real-time evaluation.
The technology is particularly useful for women with dense breast tissue, where the sensitivity of mammography is significantly reduced. Both dense glandular tissue and potential tumors appear white on a mammogram, making it difficult to distinguish an abnormality. Ultrasound uses a different mechanism, where dense tissue is echogenic (bright), while many cancers are hypoechoic (dark), allowing for better visualization.
One of the most important roles of ultrasound is its ability to differentiate between a fluid-filled cyst and a solid mass. A simple cyst, which is almost always benign, will appear on the image as an anechoic (black) structure with well-defined, smooth borders. Solid masses, whether benign or malignant, will appear with various shades of gray and a more complex internal structure.
For women with dense breasts, the addition of screening ultrasound to mammography has been shown to increase the detection of small, invasive cancers. Studies indicate that supplemental ultrasound can detect an additional three to four cancers per 1,000 women screened.
Interpreting the Images: Identifying Features of Concern
Radiologists carefully analyze several visual characteristics of a mass on an ultrasound image to determine its likelihood of being benign or malignant. Features associated with benignity suggest a low probability of cancer, typically less than two percent. These masses often appear in a round or oval shape with smooth, well-defined margins.
Benign Characteristics
A classic benign finding is a mass that is wider than it is tall, meaning its longest dimension runs parallel to the chest wall. The internal structure is usually uniform (homogeneous) and may include a thin, bright echogenic capsule around the mass. Simple cysts, a common benign finding, are entirely anechoic (black) with strong echoes behind them, known as posterior acoustic enhancement.
Malignant Characteristics
Conversely, features that raise suspicion for malignancy relate to the mass’s shape, borders, and interaction with the surrounding tissue. Malignant tumors frequently present with an irregular shape and non-circumscribed margins. The edges may appear angular, spiculated, or microlobulated, indicating that the mass is invading the adjacent tissue.
A suspicious mass often has a non-parallel orientation, meaning it is taller than it is wide. This means the dimension perpendicular to the skin is greater than the one parallel to the skin. The internal structure is often heterogeneous (mixed) and can be markedly hypoechoic (very dark).
Other Suspicious Markers
Other concerning visual markers include posterior shadowing, where the sound waves are significantly blocked by the mass, creating a dark shadow behind it. Increased blood flow (vascularity) within the mass, as visualized with Doppler ultrasound, suggests a higher metabolic rate typical of a growing cancer. When multiple suspicious features are present, the probability of the lesion being malignant rises significantly, potentially exceeding a 95 percent likelihood.
The Patient Experience and Follow-Up Actions
A breast ultrasound is a straightforward procedure performed by a sonographer or a radiologist. The patient lies on an examination table, and a water-based gel is applied to the breast to ensure good contact between the skin and the transducer. The small, handheld transducer is then gently moved across the skin to capture real-time images of the breast tissue. The process is generally painless and takes approximately 15 to 30 minutes, depending on the complexity of the findings.
Following the imaging, the radiologist interprets the results and assigns a standardized score using the Breast Imaging Reporting and Data System (BI-RADS). This system ensures consistent reporting across different facilities by categorizing findings on a scale from 0 to 6. The score provides an assessment of the likelihood of cancer and dictates the necessary next steps for patient care.
The BI-RADS categories guide follow-up actions:
- Category 1 (Negative) and 2 (Benign): Recommend routine annual screening.
- Category 3 (Probably Benign): Suggests a less than two percent chance of malignancy and recommends a short-interval follow-up ultrasound in six months to ensure stability.
- Category 4 (Suspicious) and 5 (Highly Suggestive): Usually lead to a recommendation for a biopsy. Category 4 is further subdivided (4A, 4B, 4C) to reflect the increasing probability of cancer, ranging from a low chance to a high chance.
- Category 6: Reserved for a lesion already confirmed as cancer by a prior biopsy, which is being evaluated during treatment.