Table 1.

Description of BTA U1-5 category appearances^5,6

U1	U2	U3	U4	U5
Normal	Microcystic/spongiform	Homogeneous, hyperechoic (markedly), solid, halo (follicular lesion)	Solid, hypoechoic	Solid, hypoechoic, lobulated/irregular outline, microcalcification (?papillary carcinoma)
	Halo, iso/mildly hyperechoic	?Hypoechoic, equivocal echogenic foci, cystic change	Solid, very hypoechoic	Solid, hypo-echoic, lobulated/irregular outline, globular calcification (?medullary carcinoma)
	Peripheral eggshell calcification	Mixed/central vascularity	Disrupted peripheral calcification, hypoechoic	Intra nodular vascularity
	Cystic change ± ring down sign (colloid)		Lobulated outline	Shape (taller >wide) (AP >TR)
	Peripheral vascularity			Characteristic associated lymphadenopathy