(a) A thyroid cyst. The right lobe of the thyroid is shown.
The anechoic area in the lower pole and the increased through-transmission of sound behind it are characteristic of a simple thyroid cyst. (b) A thyroid tumour. The left lobe is shown containing a solid inhomogeneous mass. The reduced echogenicity around the mass suggests the presence of a capsule. It is not possible to differentiate between a benign tumour and a malignant tumour using ultrasound scans.
