Thyroid ultrasounds serve as a common diagnostic tool for evaluating thyroid health. This non-invasive imaging technique is frequently performed when a healthcare provider identifies a thyroid nodule during a physical examination or when abnormal laboratory results suggest a thyroid issue. Patients often wonder about the ability of a thyroid ultrasound to detect cancer.
What a Thyroid Ultrasound Is
A thyroid ultrasound is a painless imaging procedure that utilizes sound waves to create real-time images of the thyroid gland and surrounding neck tissues. The thyroid gland, located in the front of the neck, is easily accessible for this type of scan, making ultrasound a preferred initial imaging test for assessing its size, shape, and any structural changes.
During the procedure, a technician applies a water-based gel to the neck, which helps transmit sound waves from a handheld wand, called a transducer, into the body. These sound waves bounce off the thyroid and other structures, and the transducer collects the echoes. A computer then processes these echoes to generate a detailed picture on a monitor, allowing medical professionals to visualize the gland and identify any abnormalities like cysts or nodules.
How Ultrasounds Identify Suspicious Growths
Ultrasound identifies specific characteristics within thyroid nodules that may suggest malignancy. Radiologists examine features to assess a nodule’s suspicion level, including its composition. Solid nodules are generally more concerning than fluid-filled cysts.
Another important feature is echogenicity, which refers to how bright or dark the nodule appears on the ultrasound image compared to the surrounding thyroid tissue; hypoechoic (darker) nodules often raise greater suspicion. The margins of a nodule are also assessed, with irregular or ill-defined borders being a potential indicator of malignancy. A shape that is “taller-than-wide” on a transverse view is another suspicious finding.
The presence of calcifications, particularly tiny bright spots known as microcalcifications, is a notable feature that increases suspicion for cancer. While some calcifications can be benign, microcalcifications are often closely associated with malignancy. Additionally, increased or chaotic blood flow within the nodule, observed through Doppler imaging, can also be a suspicious sign, though it is less specific than other features.
What Happens After a Suspicious Finding
When a thyroid ultrasound reveals a suspicious nodule, further evaluation is typically recommended to determine its nature. The primary next step often involves a fine needle aspiration (FNA) biopsy. This procedure involves using a very thin, hollow needle to collect a small sample of cells directly from the suspicious nodule.
The FNA biopsy is often performed with ultrasound guidance, which allows the healthcare provider to precisely guide the needle into the nodule, ensuring an accurate sample is obtained. The collected cells are then sent to a laboratory for pathological examination under a microscope. This microscopic analysis determines whether the cells are benign (non-cancerous) or malignant (cancerous).
Multiple samples may be taken from different parts of the nodule to ensure sufficient diagnostic material. If the initial biopsy results are inconclusive or “indeterminate,” molecular testing on the sample may be performed to further assess the risk of malignancy. In cases where the suspicion for cancer is low based on ultrasound features and nodule size, a healthcare provider might recommend monitoring the nodule with repeat ultrasounds over time instead of an immediate biopsy.
Understanding Ultrasound’s Diagnostic Limits
While a thyroid ultrasound is effective at identifying suspicious features within the thyroid gland, it cannot definitively diagnose cancer. Ultrasound is an imaging tool that provides visual information about the characteristics of nodules. It helps guide the decision of whether a nodule requires further investigation, but it does not provide a definitive cellular diagnosis.
A definitive diagnosis of thyroid cancer relies on the pathological examination of tissue. This is because even nodules with several suspicious ultrasound features can sometimes turn out to be benign. Conversely, some benign-appearing nodules might occasionally harbor malignancy, though this is less common. Therefore, the ultrasound serves as a screening and guidance tool, indicating which nodules warrant a biopsy to confirm or rule out cancer.