Ultrasound images display in shades of gray, not color. There isn’t a specific “color” that identifies malignancy. Instead, cancer’s appearance on an ultrasound relies on characteristics radiologists observe, which relate to how sound waves interact with and reflect off tissues.
How Ultrasound Imaging Works
Ultrasound imaging, or sonography, uses high-frequency sound waves to create live images of internal body structures. A transducer emits these sound waves, which travel through tissues until they encounter boundaries.
When sound waves hit these boundaries, some reflect back to the transducer as echoes. The transducer converts these echoes into electrical signals, which a computer processes to generate a two-dimensional grayscale image. The shades of gray depend on the intensity and characteristics of the returning echoes. For example, fluid-filled structures appear dark as most sound waves pass through them, while denser tissues reflect more sound waves and appear brighter.
Interpreting Ultrasound Images: What Radiologists Look For
Radiologists analyze several features within ultrasound images to assess if a mass is cancerous.
Echogenicity describes how bright or dark an area appears relative to surrounding tissue. Malignant tumors often appear “hypoechoic,” meaning darker than normal tissue because they reflect fewer sound waves. Some benign lesions might appear “hyperechoic” (brighter), though cancer can also have varied echogenicity.
The shape and margins of a lesion provide clues. Suspicious masses often have irregular shapes with ill-defined, angular, or “spiculated” margins, meaning sharp lines radiating from the mass. Benign lesions typically have smooth, well-defined, and regular margins. A “taller-than-wide” orientation can also be a suspicious finding.
Radiologists examine the mass’s internal structure, looking for calcifications (tiny mineral deposits), cystic areas, or solid regions. Malignant lesions often appear solid or have a heterogeneous internal texture. Simple cysts are typically fluid-filled and anechoic (without internal echoes). The presence and pattern of calcifications can also raise suspicion.
Vascularity, or blood flow within and around the lesion, is assessed using Doppler ultrasound. Malignant tumors often exhibit increased blood flow due to rapid and abnormal vessel formation, appearing as irregular or chaotic flow patterns. This increased vascularity is an indicator, though some benign conditions can also show increased flow.
The compressibility or stiffness of the tissue can be evaluated. Malignant lesions tend to be stiffer and less compressible when pressure is applied with the ultrasound probe. Benign lesions are often softer and more easily deformed. Radiologists evaluate a combination of these features to determine the likelihood of malignancy.
Beyond Ultrasound: Comprehensive Cancer Diagnosis
An ultrasound is an initial diagnostic tool to identify suspicious areas, but it is rarely the sole basis for a cancer diagnosis. Clinical symptoms and a patient’s medical history are always considered alongside imaging findings. For instance, a lump detected by a patient or during a physical exam might prompt an ultrasound.
If ultrasound findings are concerning, further imaging may be necessary to gather more information. Computed tomography (CT) scans and magnetic resonance imaging (MRI) can provide more detailed anatomical views. These help determine the extent of a potential tumor or its spread and complement ultrasound information.
Ultimately, a biopsy is almost always required for a definitive cancer diagnosis. This involves removing a small tissue sample from the suspicious area. A pathologist, a doctor specializing in diagnosing diseases by examining tissues, then scrutinizes this sample under a microscope for cancer cells. This collaborative process between radiologists and pathologists is fundamental to accurate diagnosis and guiding treatment decisions.