Compare the two series of pictures. Hashimoto's thyroiditis frequently has 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, the hypoechogenic areas in most of the Hashimoto's cases have irregular but sharp borders. In the cases demonstrated above, the only difference between the ultrasound appearance is the pattern of the hypoechogenic areas. These foci are more blurred in the case of subacute thyroiditis. Nevertheless, the sonographic pattern itself is not diagnostic.