When a breast ultrasound is performed, a common finding is a hypoechoic lesion. While this term can cause concern, many such findings are not malignant. Understanding hypoechoic lesions and their characteristics, including size, can clarify this common imaging result. This article explains hypoechoic lesions and the factors radiologists consider during evaluation.
Understanding Hypoechoic Breast Lesions
In medical imaging, “hypoechoic” describes an area that appears darker than the surrounding tissue on an ultrasound scan. This visual difference occurs because the lesion reflects fewer sound waves back to the ultrasound transducer compared to the adjacent breast tissue. A “lesion” is a general term for any abnormal area identified during an examination.
Hypoechoic breast lesions can appear as various shapes and textures on the ultrasound screen. The appearance depends on the internal composition of the lesion. For instance, fluid-filled structures like cysts or solid masses with a lower density or different cellular arrangement than normal tissue tend to appear hypoechoic.
The Role of Size and Other Ultrasound Features
There is no single “normal size” for a hypoechoic lesion that definitively determines if it is benign or malignant. Size alone is not diagnostic, as both benign and malignant lesions can vary significantly in dimensions. Instead, radiologists evaluate size as one component within a broader set of ultrasound features to form a comprehensive assessment.
Other characteristics assessed alongside size include the lesion’s shape (oval, round, or irregular) and margins (smooth/well-defined or ill-defined/spiculated). A lesion’s orientation (wider than tall or taller than wide) provides another clue. Radiologists also observe posterior acoustic features, such as enhancement (brighter area behind) or shadowing (darker area behind), which indicate how sound waves pass through the mass. The presence or absence of blood flow within the lesion, known as vascularity, is evaluated using Doppler ultrasound.
Common Types of Hypoechoic Lesions
Many types of breast lesions can appear hypoechoic on ultrasound. Simple cysts, which are fluid-filled sacs, are a common benign finding. They typically appear round or oval with smooth margins and often exhibit posterior acoustic enhancement. While they can range in size, a simple cyst is generally considered benign regardless of its dimensions.
Fibroadenomas are another frequent benign cause of hypoechoic lesions, often appearing oval or gently lobulated with smooth or macrolobulated margins. These solid masses are usually wider than tall and can vary from a few millimeters to several centimeters. Intramammary lymph nodes, normal breast lymph glands, also appear hypoechoic, typically oval with a visible fatty center (hilum) and are usually small.
Conversely, malignant lesions, such as invasive ductal carcinoma, often present as hypoechoic masses with irregular shapes and spiculated or ill-defined margins. These lesions may appear taller than wide and can cause posterior acoustic shadowing. Increased vascularity within the lesion can also be a feature of malignancy, though size varies considerably with malignant lesions, and growth over time is a concern.
What Happens After a Hypoechoic Lesion is Found?
After a hypoechoic lesion is identified, radiologists use the Breast Imaging Reporting and Data System (BIRADS) to categorize the findings and recommend appropriate next steps. This standardized system assigns a number, such as BIRADS 2 (benign), BIRADS 3 (probably benign, short-interval follow-up suggested), or BIRADS 4 (suspicious, biopsy considered). While size can influence the BIRADS category, it is the combination of all ultrasound features that primarily guides this classification.
For lesions categorized as BIRADS 3, follow-up imaging, typically another ultrasound, may be recommended at short intervals to monitor for any changes in size or characteristics. A biopsy might be recommended for lesions classified as BIRADS 4 or 5, or if a BIRADS 3 lesion shows concerning changes over time. A biopsy involves taking a tissue sample for microscopic examination to obtain a definitive diagnosis. It is important to discuss specific findings and recommendations with a healthcare provider for personalized guidance.