Both cases present an atypical pattern. The risk of a follicular tumor is apparently higher in the left case characterized by atypical microfollicular proliferation. The pattern demonstrated right is more close to a hyperplastic nodule than to a follicular tumor. Nevertheless, the mild pleomorphism, the presence of irregular, abortive microfollicles raised the suspicion of carcinoma.

The ultrasound presentation of the left case is deceptive: a relatively large solitary nodule presenting a halo is more likely an adenoma than a hyperplastic nodule. There was one ultrasound sign standing against a follicular tumor: the large lesion was composed of smaller, discrete areas.
The left case corresponds to a follicular-type tumor because it is solitary, large, presents halo and perinodular blood flow. Moreover, the nodule is suspicious because of the presence of microcalcifications.