Hypoechoic nodules cast off fewer or weaker echos than the surrounding normal tissue, while hyperechoic nodules cast more or stronger echos than the surrounding normal tissue.
Typically, benign thyroid nodules appear hyperechoic on the sonogram, while malignant (cancerous) thyroid nodules are more likely to be hypoechoic, casting off fewer or weaker echos.
However, the chance of any hypoechoic nodule being cancerous is still very low, because benign thyroid nodules are much more common.
If a thyroid nodule requires further evaluation, the next step is generally to perform a fine needle aspiration (FNA) of the suspicious nodule, a test in which a thin needle is inserted into the nodule to extract cells for evaluation. Looking at these cells under a microscope helps to determine whether or not the nodule contains cancer cells.
at 12:20 AM on Jun. 3, 2011