Solid hypoechoic with ≥1 suspicious feature (microcalcifications, taller-than-wide, irregular margins, microlobulated, extrathyroidal extension).

Solid hypoechoic with smooth margins, NO microcalcifications, NO extrathyroidal extension, NOT taller-than-wide.

Isoechoic or hyperechoic solid nodule, OR partially cystic with eccentric solid areas (without suspicious features).

Spongiform or partially cystic without any suspicious sonographic features.

Purely cystic nodule without solid component.