Ultrasonic evaluation of benign and malignant nodules in echographically multinodular thyroids.

In 165 patients with ultrasound findings of multinodular thyroids in whom thyroid resection was performed, sonographic features and pathohistologic findings of removed nodules were analyzed. Of 426 nodules removed, 70 were carcinomas and 356 benign. Carcinomas are more often hypoechogenic (p < 0.01) and contain nodular calcifications (p < 0.01), while benign nodules are more often iso-hyperechogenic (p < 0.01), showing intranodular cystic degenerative changes (p < 0.01) and perinodular hypoechogenic rim (p < 0.01). Mean diameter of carcinomatous nodules is lower than in benign nodules (p = 0.022). The relative proportion of malignant nodules is highest in the upper halves of thyroid lobes (p < 0.01). Although certain sonographic signs increase the likelihood of a given lesion being malignant or benign, the lack of absolute specificity in the ultrasound evaluation of thyroid nodules was confirmed.