Table 2. US Features Predicting Malignant Thyroid Nodules According to Combination of Solidity and Echogenicity.

Solidity and Echogenicity	US Features	No. of Benign Nodules	No. of Malignant Nodules	P	Multivariable Analysis
					Odds Ratio (95% CI)	P
All (n = 902)	Overall	636 (70.5)	266 (29.5)
	Solid	462 (64.6)	253 (35.4)	< 0.001	1.92 (0.93–3.97)	0.077
	Hypoechoic	224 (47.3)	250 (52.7)	< 0.001	10.35 (5.79–18.51)	< 0.001
	Irregular shape	24 (3.8)	25 (9.4)	0.001	0.35 (0.16–0.78)	0.009
	Microcalcification	73 (38.6)	116 (61.4)	< 0.001	3.58 (2.29–5.61)	< 0.001
	Non-parallel orientation	75 (34.7)	141 (65.3)	< 0.001	3.54 (2.23–5.60)	< 0.001
	Spiculated/microlobulated margin	27 (16.8)	134 (83.2)	< 0.001	6.29 (3.73–10.62)	< 0.001
	Comet tail artifact	37 (5.8)	0 (0.0)	< 0.001	N/A	0.998
	Spongiform	24 (3.8)	0 (0.0)	0.001	N/A	0.998
Solid hypoechoic (n = 436)	Overall	194 (44.5)	242 (55.5)
	Irregular shape	22 (46.8)	25 (53.2)	0.735
	Microcalcification	37 (25.9)	106 (74.1)	< 0.001	3.46 (2.11–5.67)	< 0.001
	Non-parallel orientation	41 (23.0)	137 (77.0)	< 0.001	3.55 (2.19–6.76)	< 0.001
	Spiculated/microlobulated margin	24 (15.9)	127 (84.1)	< 0.001	4.99 (2.93–8.50)	< 0.001
	Comet tail artifact	2 (100.0)	0 (0.0)	0.197
	Spongiform	0 (0.0)	0 (0.0)	N/A
Partially cystic or isohyperechoic (n = 466)	Overall	442 (94.8)	24 (5.2)
	Irregular shape	2 (100.0)	0 (0.0)	1.000
	Microcalcification	36 (78.3)	10 (21.7)	< 0.001	0.21 (0.07–0.58)	0.003
	Non-parallel orientation	34 (89.5)	4 (10.5)	0.118	1.13 (0.21–5.98)	0.889
	Spiculated/microlobulated margin	3 (30.0)	7 (70.0)	< 0.001	0.03 (0.01–0.14)	< 0.001
	Comet tail artifact	35 (100.0)	0 (0.0)	0.242
	Spongiform	24 (100.0)	0 (0.0)	0.626

Numbers in parentheses are percentages. Malignant US features were indicated by spiculated/microlobulated margin, non-parallel orientation, and microcalcifications. CI = confidence interval, US = ultrasonography