A low density nodule is an imaging diagnosis that refers to a nodule that has a low density relative to a normal organ. Low-density nodule is mainly after ultrasound, CT, MRI and other imaging examinations, a description of the human body mass, relative to the normal organs of low density, may be cysts, there may also be malignant tumors. In the clinical ultrasound, CT and other examinations, for low density nodules can not confirm its specific nature, need to do enhanced CT or MRI examination to determine the size of the nodule, border, internal echo, blood supply and so on, through the enhancement of the judgment, whether there is the possibility of malignant tumors, but the final diagnosis still need to be based on the pathology of the test to confirm the diagnosis. If low-density nodules are found in the clinic, it is recommended to consult the relevant departments of regular hospitals, such as thyroid nodules need to consult the thyroid surgery department.