Atypical thyroid cancers on sonography

The management of thyroid nodules is a common clinical problem. Thyroid nodules are present in up to 50% of the adult population. However, thyroid malignancy is rare, occurring in only 5% to 15% of nodules. Although certain specific patterns on imaging are almost always indicative of benignity, there is considerable overlap between the sonographic appearances of benign and malignant nodules. Radiologists should be wary of applying pattern recognition approaches too liberally as some malignant nodules may exhibit sonographic features more commonly associated with benign nodules such as cystic change, comet-tail artifact, smooth margins, echogenic echotexture, hypoechoic halos, or peripheral calcifications. This article illustrates atypical imaging appearances of thyroid malignancies and reviews recent literature in an attempt to clarify nuances in the diagnosis of malignancy in benign-appearing nodules.