First, please compare the images of low power field: although both cases present a very cellular pattern, hyperplastic nodule is characterized by the presence of isolated nuclei while follicular tumor is by microfollicles. It is worth to compare the microfollicles. In the event of follicular tumor a regular round structure can be observed while in hyperplastic nodule, the microfollicle is not regularly round.
In contrast with the monomorphous pattern of follicular tumor, hyperplastic nodule presents a moderate degree of anisonucleosis.

There were multiple nodules in the left case. The largest hypoechogenic one displayed both a halo and a perinodular blood flow. This combination, i.e. a not solitary and relatively not large nodule presenting halo and perinodular blood flow adds little to the differential diagnostics because both a hyperplastic nodule and a follicular tumor have to be involved with similar probability.
As regards the right case, a relatively large and solitary nodule displayed perinodular blood flow while the presence of a halo is doubtful. This ultrasound presentation is itself not fully pathognomic, however stands strongly for a follicular type tumor.