Ultrasound images display in shades of gray, not specific colors. Therefore, a tumor does not have a characteristic color on an ultrasound. Instead, medical professionals interpret visual and dynamic characteristics in these grayscale images to assess a mass.
How Ultrasound Images Are Formed
Ultrasound imaging, also known as sonography, relies on high-frequency sound waves to generate internal body images. A handheld device called a transducer emits these sound waves into the body, which then travel through tissues. As sound waves encounter different structures, such as organs, fluids, or masses, they reflect back to the transducer.
The transducer receives these reflected sound waves and converts them into electrical signals. A computer then processes these signals to create a real-time image on a monitor.
The brightness of each point depends on how strongly sound waves are reflected, a property called echogenicity. Different tissue densities and compositions reflect sound waves differently, resulting in variations in brightness. For instance, fluid-filled structures tend to appear black (anechoic) because they transmit most sound waves, while denser structures reflect more waves and appear brighter.
Visual Characteristics of Tumors
Sonographers and radiologists assess visual features of a mass to determine its nature. Echogenicity, describing how bright or dark a mass appears compared to surrounding tissues, is one important characteristic. A mass can be hypoechoic (darker), hyperechoic (brighter), or isoechoic (similar in brightness) relative to the adjacent tissue. Malignant tumors often appear hypoechoic due to their dense cellular composition, while benign masses are often hyperechoic or isoechoic.
Shape and margins also provide important clues. Benign masses often have well-defined, smooth, and regular shapes, such as oval or round. In contrast, malignant tumors often exhibit irregular, ill-defined, or spiculated (spiky) margins, indicating potential infiltrative growth into surrounding tissues.
Internal texture can be homogeneous (uniform) or heterogeneous (mixed). Malignant masses often display a heterogeneous texture, suggesting an abnormal and varied internal structure. Calcifications or cystic components within a mass can also be evaluated; microcalcifications are sometimes associated with malignancy.
Beyond Visuals: Dynamic Assessment
Beyond static visual characteristics, dynamic assessments offer additional information about a mass. Doppler ultrasound is a technique that evaluates blood flow within a lesion. Malignant tumors often exhibit increased and chaotic blood flow patterns, referred to as hypervascularity, due to their rapid growth and the formation of new, abnormal blood vessels. Benign masses, conversely, often show minimal or peripheral blood flow. Analyzing these vascular patterns helps differentiate between benign and potentially malignant lesions.
Other dynamic properties include compressibility and elasticity. Compressibility refers to whether a mass changes shape or size when pressure is applied by the transducer. Benign masses are often mobile and compressible, while malignant masses tend to be fixed and rigid, indicating invasion into surrounding tissues.
Elastography, a specialized technique, measures tissue stiffness or elasticity. Malignant tumors are often stiffer than benign ones due to their dense cellular structure and altered extracellular matrix. These dynamic assessments provide a more comprehensive understanding of a mass’s biological behavior.
Ultrasound’s Place in Diagnosis
Ultrasound serves as a valuable tool for initial assessment and screening, including for tumors. It is a non-invasive, widely available, and quick imaging modality that differentiates between fluid-filled cysts and solid masses. Its real-time imaging also makes it useful for guiding procedures like biopsies.
Despite its utility, ultrasound alone is rarely definitive for diagnosing cancer; it identifies suspicious characteristics but cannot conclusively determine if a mass is cancerous. A comprehensive diagnosis often requires interpretation by a radiologist or sonographer, who considers all ultrasound findings in conjunction with a patient’s medical history. Further diagnostic steps, such as other imaging modalities like MRI or CT scans, laboratory tests, and a biopsy for tissue analysis, are often necessary to confirm a diagnosis.