Solid and Isoechoic Thyroid Nodules Without Malignant Sonographic Features: Comparison of Malignancy Rate According to Nodule Size, Shape and Color Doppler Pattern

This study aimed to assess the malignancy rate of solid and isoechoic thyroid nodules without malignant sonographic features (SITNs) and to compare the malignant and benign SITNs according to nodule size, shape and color Doppler pattern. Of 382 SITNs with the largest diameter ≥10 mm, nodule size, nodule shape (i.e. spherical vs. ovoid) and color Doppler pattern (i.e. scant, peripheral, central, and mixed type) of each nodule were retrospectively evaluated. A total of 114 SITNs were histopathologically confirmed by surgery (called surgical SITN) and the malignancy rate of surgical SITNs was 8.8% (10/114). There was no statistical association between the incidence of malignancy of SITNs and nodule size but the malignancy rate of spherical SITNs was higher than that of ovoid SITNs. A significant relationship between peripheral vascularity of SITNs and benignity was found but the other vascularity patterns showed no significant association with malignancy or benignity of SITNs.