Sonographic Features of Follicular Variant Papillary Thyroid Carcinomas in Comparison With Conventional Papillary Thyroid Carcinomas

Objective. The purpose of this study was to compare the sonographic features as well as the results of fine-needle aspiration biopsy (FNAB) of follicular variant papillary thyroid carcinoma (FVPTCs) and conventional papillary thyroid carcinoma (PTCs), Methods. Forty patients with 44 FVPTCs and 59 patients with 74 conventional PTCs were enrolled in this study. The sonographic features, sonographic gradings, and FNAB results were compared between the two groups. Results. The mean nodule size of FVPTCs was larger than that of conventional PTCs (17.70 versus 10.53 mm; P < .001). Sonographic features of an ovoid-to-round shape (95% versus 73%), isoechogenicity (52% versus 8%), and a hypoechoic halo (25% versus 3%) were more frequent in FVPTCs than conventional PTCs (P < .001). Sonographic features of a taller-than-wide shape (5% versus 22%), a spiculated margin (7% versus 32%), marked hypoechogenicity (5% versus 38%), and microcalcification (7% versus 24%) were rarer in FVPTCs than conventional PTCs (P < .05). The incidence of a sonographically malignant grade was also lower in FVPTCs (48%) than conventional PTCs (81%; P < .001). A diagnosis of PTC on FNAB of FVPTCs was less common than that of conventional PTCs (28% versus 56%; P = .0393); however, a diagnosis of an indeterminate cytologic type such as atypical cells or follicular lesions in FVPTCs was higher than that in conventional PTCs (46% versus 19%; P = .0418). Conclusions. Follicular variant papillary thyroid carcinomas show a relatively larger size, more benign sonographic features, a lower incidence of a sonographically malignant grade, and a lower diagnostic rate of PTC on FNAB compared with conventional PTCs.