Thyroid nodules with discordant results of ultrasonographic and fine-needle aspiration findings

As the detection of thyroid nodules increases, it is important to differentiate whether thyroid nodules are malignant or not. Ultrasonography-guided fine-needle aspiration cytology is the standard method to diagnose thyroid nodules. Ultrasonographic findings of thyroid nodules can predict the risk of malignancy, and fine-needle aspiration allows the examination of cytopathology of thyroid nodules. However, both are not perfect, with a certain degree of false negative or false positive results. Therefore, we can face thyroid nodules with discordant results of ultrasonographic and fine-needle aspiration findings. In the case of benign features on ultrasonography with malignant cytology, follicular thyroid cancer, follicular variant papillary thyroid cancer, cystic or degenerative changes of thyroid cancer, and thyroiditis are candidates for diagnosis. In contrast, for the nodules with ultrasonographic features of highly suspicious of malignancy but benign cytology, we can consider the possibility of thyroiditis, changes of benign nodule, and cystic changes of thyroid cancer. These various conditions may result in discordant results of ultrasonographic features and fine-needle aspiration cytology, which need special attention not to miss the diagnosis of malignant nodules.