A very hypoechoic thyroid nodule is a nodule that echoes below the cervical band of muscle and is a suspected sign of malignancy on ultrasound. Thyroid nodules are thyroid masses detected by palpation or imaging such as ultrasound, and are imaging manifestations of many benign and malignant thyroid diseases. Thyroid nodules can be characterized by their echogenicity and other features to determine the risk of malignancy. The echogenicity of a thyroid nodule is based on the surrounding thyroid tissue, with echoes below the thyroid parenchyma and above the cervical striated muscle being hypoechoic, and echoes below the cervical striated muscle being extremely hypoechoic. Both very hypoechoic and hypoechoic nodules are signs of suspected malignancy, i.e., there is some risk that they are the result of a malignant tumor of the thyroid gland. Extremely hypoechoic nodules of the thyroid gland may be the result of malignant tumors such as thyroid cancer and thyroid lymphoma, or they may be the result of benign thyroid diseases such as some cases of Hashimoto’s thyroiditis and nodular goiter. Patients are advised to consult a specialist to determine the risk of malignancy based on the size of the nodule, calcification, and imaging grading, and to follow the doctor’s instructions for further investigation and treatment.