Table 1.

Diagnostic accuracy of preoperative ultrasound for extrathyroidal extension in thyroid cancer.

References	Country	Study	Patients	Criteria	SE (%)	SP (%)	PPV (%)	NPV (%)	AC (%)
Shimamoto et al. (26)	Japan	SR	35 of 77 with ETE (minimal and gross)	A	80	73.8	71.8	81.6	76.6
Tomoda et al. (27)	Japan	SR	13 of 509 with TI	C	91	93	25	99	93
Kwak et al. (28)	South Korea	SR	89 of 221 with ETE (N/A)	A	65.2	81.8	70.7	77.7	N/A
Kim et al. (29)	South Korea	SR	67 of 75 with ETE (minimal and gross)	A,C,D	78.5	79.5	46.8	94.1	79.3
Lee et al. (30)	South Korea	SR	174 of 377 with ETE (N/A)	A	66.1	65.1	72.2	58.3	N/A
Lee et al. (31)	South Korea	SR	275 of 568 with ETE (minimal and gross)	A	83.3	68.9	71.6	81.5	75.9
Moon et al. (32)	South Korea	SR	26 of 105 with EFI	E	46.2	97.5	85.7	84.6	84.8
Kamaya et al. (33)	USA	SR	16 of 62 with ETE (minimal and gross)	A,B	25	93	57	78	N/A

Criteria category: A: focal bulging out or disruption of the thyroid capsule by tumor or more than 25% of perimeter of the tumor was abutting the thyroid capsule; B: vessels extending to or from the nodule were seen beyond the capsule on either color or power Doppler images; C: the absence of a clear adventitia, dilatation of the cartilage space or tumor extension into the space, or irregularity of the tracheal mucosa; D: loss of normal esophageal layer by tumor, the tumor was in contact with 180° or more of the circumference of the vessel and tumor invasion into the vessels lumen or a tumor occupying the tracheal esophageal groove; E: the loss of echo-genic perithyroidal fat tissue by tumor. SR, single center retrospective; ETE, extrathyroidal extension; TI, trachea invasion; EFI, extrathyroidal fat invasion; SE, sensitivity; SP, specificity; PPV, positive predictive value; NPV, negative predictive value; AS, accuracy; N/A, not available.