| Ultrasonographic Pattern | Ultrasonographic Characteristics | Estimated Risk of Malignancy | Size to perform FNAB |
| High Risk | Hypoechoic, solid nodules, or nodules with mixed components (solid and partially cystic hypoechoic nodule) with one or more of the following characteristics: irregular margins (infiltrative, microlobed), microcalcifications, taller than wide, calcifications on the edge of the cyst, evidence of extra thyroid extension | Greater than 70% - 90% | FNAB is recommended if its dimensions are equal to or greater than 1.0 cm |
| Intermediate Risk | Hypoechoic solid nodule with smooth (regular) margins without microcalcifications, no evidence of extra thyroid extension, and the shape is not taller than wide | 10% al 20% | FNAB is recommended if its dimensions are equal to or greater than 1.0 cm |
| Low Risk | Isoechoic or hyperechoic solid nodule, or partially cystic nodule with eccentric solid areas, no microcalcification, no irregular margin, no evidence of extra thyroid extension, no taller than wide | 5% al 10% | FNAB is recommended if its dimensions are equal to or greater than 1.5 cm |
| Very Low Risk | Spongiform or partially cystic nodules without any of the ultrasonographic features described in low, intermediate, or high suspicion patterns | Less than 3% | FNAB can be considered if its dimensions are equal to or greater than 2.0 cm Observation without BAAF is also reasonable |
| Benign | Purely cystic nodules (without solid component) | Less than 1% | Do not perform FNAB |