To compare the gray-scale and color or power Doppler ultrasonographic (US) features according to the histological subtypes of a papillary thyroid carcinoma (PTC).

The gray-scale and color or power Doppler US features of 159 surgically confirmed PTC (classic type of PTC, 69; classic type of papillary microcarcinoma [PMC], 67; and follicular variant of PTC [FVPTC], 23) in 118 patients were analyzed retrospectively. The following US characteristics were evaluated: the type of vascularization, echogenicity, outline, ratio of anteroposterior/transverse (AP/T) diameters, as well as the presence or absence of halo signs, cystic changes, and microcalcification.

The most common type of vascularization was penetrating or central (75.4%) for the classic type of PTC, avascular (56.7%) for PMC, and peripheral and central (82.6%) for FVPTC. The echogenicity was most commonly hypoechoic (47.8%) for the classic type, hypoechoic (74.6%) for PMC, and isoechoic (30.4%) for FVPTC. The outline was most often irregular (60.9%) for the classic type, irregular (86.6%) for PMC, and regular (91.3%) for FVPTC. The ratio of the AP/T diameters was 1.0 or more in 31.9%, 55.2%, and 13.0%, a halo sign was observed in 30.4%, 6.0%, and 78.3%, cystic changes was present in 1.4%, 0%, and 21.7%, and microcalcifications were present in 55.1%, 28.4%, and 13.0% of those with the classic type, PMC, and FVPTC, respectively.

The gray-scale and color Doppler US features corresponding to the histological subtypes of PTC are significantly different from one another. The US features of FVPTC appear to be significantly different from the other subtypes in that they tend to have more benign US characteristics than those of the classic type or PMC.