Compare the two series of pictures. Hashimoto's thyroiditis has frequently a similar appearance as observed in the case of de Quervain's thyroiditis. The patchy appearance i.e. hypoechogenic areas within an echonormal background is observed in around 70% of the former, while in more than 90% of the latter disease. In contrast with subacute thyroiditis, in most Hashimoto's cases the hypoechogenic areas have irregular but sharp borders. In these cases demonstrated above, the only difference in the ultrasound appearance is the pattern of the hypoechogenic areas. In the case of subacute thyroiditis these foci are more blurred. Nevertheless, the sonographic pattern itself is not diagnostic.