US NODULE FEATURE | DEFINITION | REFERENCE |
HYPOECHOIC | Hypoechogenicity lower than thyroid parenchyma. Includes mild hypoechogenicity (lower than thyroid parenchyma but higher than strap muscle that surrounds it), moderate hypoechogenicity (similar to the muscle that surrounds it), marked hypoechogenicity (higher than the surrounding muscle. Hypoechogenicity associated with subsequent acoustic reinforcement is not included. | [14] [15] [16] |
SOLID | More than 90% of the consistency of the nodule is solid. | [16] |
IRREGULAR MARGINS | Irregular or lobed margins. No demarcation can be seen in more than 50% of the limits of the nodule. | [8] [10] [15] [17] |
ABSENCE OF A HALO | Unidentifiable hypoechogenic halo that surrounds nodule or parenchyma. | [4] [18] |
DIAMETER ≥ 10 MM | Size of the diameter of the nodule greater than 10 millimeters in the decimal system. | [19] |
MICROCALCIFICATIONS | Internal or peripheral hyperechogenic points less than 2 mm with/without acoustic shadow. Associated to or immersed in liquid or colloidal tissue are not included. | [17] [20] |
CENTRAL FLOW/INTRANODULAR VASCULAR FLOW | Any degree of intranodular vascular flow present. | [21] [22] |