Benign, isoechoic thyroid nodule with cystic degeneration and ill-defined margins

Ill-defined or blurred margins in a benign nodule. In the areas of cystic degeneration, the nodule margins are clearly defined and regular (arrowheads). In the isoechoic solid components of the nodule, the margins are ill-defined due to the similarity in echotexture to the surrounding thyroid parenchyma (arrows).