Breast cancer remains a significant health concern globally, with early detection playing a substantial role in improving outcomes. Various imaging techniques, including mammography, MRI, and ultrasound, aid in identifying potential abnormalities within breast tissue. This article focuses on understanding how breast ultrasound images contribute to the detection and characterization of potential breast cancer.
How Breast Ultrasound Works
A breast ultrasound machine operates by emitting high-frequency sound waves into the body, which then bounce off tissues and organs. These returning echoes are captured by the same transducer, a handheld device, and converted into electrical signals. A computer then processes these signals to generate real-time images displayed on a monitor, showing the internal structures of the breast.
Ultrasound serves as a valuable supplementary tool to mammography, particularly for individuals with dense breast tissue, where mammograms may be less effective at revealing abnormalities. It can also be a primary imaging method for evaluating specific symptoms, such as a palpable lump, or for younger patients, reducing exposure to radiation. During the procedure, a clear gel is applied to the skin over the breast, and the sonographer gently moves the transducer across the area of interest to capture images from different angles.
Key Features of Malignant Tumors on Ultrasound
Radiologists examine specific sonographic characteristics when identifying malignant lesions on breast ultrasound. Malignant tumors often display an irregular or angular shape, sometimes appearing with spiky extensions known as spiculations that radiate from the mass. The margins of these lesions tend to be ill-defined, indistinct, or microlobulated, making it difficult to determine their exact boundaries.
Another feature is an orientation where the lesion appears “taller-than-wide,” meaning its anteroposterior dimension is greater than its transverse measurement. Malignant masses are typically hypoechoic, appearing darker than the surrounding normal breast tissue on the ultrasound image because they transmit fewer sound waves. Posterior shadowing, where sound waves are blocked by the dense tumor, creating a dark area behind the lesion, is also a common indicator. Doppler ultrasound can reveal increased blood flow within or around the lesion, indicating active growth.
Differentiating Benign from Malignant Findings
Not all breast masses are cancerous; ultrasound helps distinguish between benign and malignant findings. Benign lesions often present with an oval, round, or gently lobulated shape, appearing distinctly different from the irregular shapes of malignant tumors. Their margins are typically well-defined and smooth, allowing for a clear demarcation from the surrounding tissue.
The orientation of benign masses is commonly “wider-than-tall,” with their transverse dimension exceeding the anteroposterior measurement. These non-cancerous findings can be isoechoic or hyperechoic, appearing similar to or brighter than the surrounding breast tissue. Instead of shadowing, benign lesions may exhibit posterior enhancement, where sound waves pass through easily, creating a brighter area behind the mass. Furthermore, benign lesions are often mobile when gently pressed with the transducer during the examination.
Next Steps After an Ultrasound
Following a breast ultrasound, findings are categorized using the Breast Imaging-Reporting and Data System (BI-RADS), which assigns a numerical score from 0 to 6 to indicate the level of suspicion. A BI-RADS category of 0 means the assessment is incomplete, while categories 4 or 5 suggest a suspicious or highly suggestive finding requiring further investigation. An ultrasound is often not definitive on its own and may lead to additional diagnostic steps.
Further imaging, such as magnetic resonance imaging (MRI), may be recommended to gain more detailed information about the suspicious area. A biopsy, such as a core needle biopsy or vacuum-assisted biopsy, is frequently performed to obtain tissue samples for microscopic examination and a definitive diagnosis. In some cases, routine follow-up scans may be advised to monitor stable benign-appearing findings over time. It is important to acknowledge that ultrasound has limitations, including its operator dependence and its reduced ability to detect certain types of breast cancer or microcalcifications.