Most malignant thyroid nodules are surgically treated. This report reviews changes in size of malignant thyroid nodules; none of them received any medical and surgical treatment. Three hundred and three nodules were diagnosed as malignant using fine needle aspiration biopsy (FNAB) and ultrasonography from 1997 to 2003. In 17 patients (19 nodules), they were observed for more than 6 months. We examined the transition of their major axis by ultrasonography. Large nodules (>10mm) and nodules in younger patients (age<50) tend to increase in size. As compared with benign nodules, malignant nodules tend to increase in large nodules (>10mm).
