Due to the widespread use of neck ultrasonography, physicians often encounter thyroid nodules in daily clinical settings. Most of them are benign such as adenomatous goiter or follicular adenoma; however, some malignant tumors can be contaminated. Thyroid malignancies are classified into several histological varieties including papillary, follicular, anaplastic, medullary thyroid carcinomas and so on. Each histological type of thyroid carcinoma has distinct biological characteristics and should be diagnosed and treated differentially. The majority of thyroid cancers fortunately have a favorable prognosis, while some of them need a multidisciplinary treatment by specialists. In order to minimize patients' anxiety, physicians have to be knowledgeable about these features and discriminate risky tumors from others properly.