Characteristic Dynamic Enhancement Pattern of MR Imaging for Malignant Thyroid Tumor. Preliminary Report

The purpose of this study was to determine the characteristic dynamic enhancement pattern of MR imaging for malignant thyroid tumor. Eight patients were collected, who had pathology confirmed malignant thyroid tumor preoperatively. There were five papillary carcinomas, one medullary carcinoma, one follicular carcinoma and one FNAB proven atypical cell. All images were obtained with a 3.0-T MR imaging system with and without iv contrast administration. Pathologic report and US imaging finding were collected retrospectively. Based on preoperative MR imaging, we compared dynamic MR enhancement pattern relating to pathologic type. All biopsy proven malignant thyroid tumors show hypoechogenicity on previous US imaging, except one follicular carcinoma (isoechogenicity). On T1-weighted images, one papillary carcinoma showed high SI and one medullary carcinoma showed low SI. The other cases were not differentiated with normal parenchyma. On T2-weighted images, three papillary carcinomas and one follicular carcinoma showed high SI and one papillary carcinoma showed low SI. The other case was not differentiated with normal parenchyma. On contrast agent-enhanced dynamic T1WI, five papillary carcinomas and one medullary carcinoma showed delayed enhancement compared to normal parenchyma. One follicular carcinoma showed stronger enhancement than normal parenchyma, one papillary carcinoma showed persistently decreased enhancement than normal parenchyma. Although this study is limited by the small patient population, the data suggest that delayed enhancement on enhanced dynamic T1WI may be a characteristic MR finding of malignant thyroid tumor.