Ultrasound is a valuable tool in examining lymph nodes, but it generally does not provide a definitive diagnosis of cancer on its own. It serves as an initial assessment and screening method that can identify features in lymph nodes that warrant further investigation.
Understanding Ultrasound Technology
Ultrasound imaging utilizes high-frequency sound waves to generate real-time images of internal body structures. A transducer emits these sound waves into the body. When the sound waves encounter boundaries between different tissues, such as between fluid and soft tissue or soft tissue and bone, some of them reflect back to the transducer as echoes.
The transducer then captures these returning echoes and sends them to a computer. The computer processes the information to create a visual representation of the tissues and organs. This technology is particularly effective for visualizing soft tissues, including lymph nodes, and is considered safe because it does not use ionizing radiation.
Identifying Suspicious Lymph Nodes
When examining lymph nodes with ultrasound, medical professionals look for specific characteristics that may suggest the presence of cancer. Normal, benign lymph nodes typically appear oval or bean-shaped and often have a bright, central area known as a fatty hilum. This hilum represents normal lymph node architecture.
Suspicious lymph nodes might show changes in their appearance. They can become enlarged, often exceeding 10mm in their short axis diameter, and may lose their typical oval or bean shape, becoming more rounded. The internal structure might also change, with a loss of the fatty hilum or a heterogeneous, less uniform appearance. Increased or abnormal blood flow patterns, particularly peripheral or mixed vascularity rather than the usual central hilar flow, can also be a sign of malignancy. Additionally, features like calcifications or areas of necrosis (tissue death) within the lymph node can raise suspicion for cancer.
Why Ultrasound Isn’t Always Definitive
While ultrasound is highly effective at identifying suspicious features in lymph nodes, it cannot definitively diagnose cancer. The characteristics that suggest malignancy on ultrasound, such as enlargement, round shape, or loss of the fatty hilum, can also be present in benign conditions. For instance, infections or inflammation can cause lymph nodes to swell and exhibit abnormal appearances, mimicking cancerous changes. This overlap in appearance means that a suspicious ultrasound finding does not automatically confirm cancer.
Furthermore, ultrasound has limitations in detecting very small cancerous deposits or early-stage disease within lymph nodes. The accuracy can also be influenced by the skill of the sonographer performing the examination.
Beyond the Ultrasound What Comes Next
If an ultrasound reveals suspicious lymph node characteristics, further diagnostic procedures are typically necessary to determine if cancer is present. The primary next step is often a biopsy, which involves obtaining a tissue sample from the suspicious lymph node for microscopic examination. This is the only definitive method for diagnosing cancer in lymph nodes.
Common biopsy procedures include fine needle aspiration (FNA) or excisional biopsy. FNA involves inserting a thin needle into the lymph node to withdraw cells, often guided by ultrasound. An excisional biopsy involves surgically removing the entire lymph node for analysis. Depending on the findings, additional imaging tests like CT, MRI, or PET scans might also be recommended to assess the extent of any disease.