Detection of medullary thyroid carcinoma and regional lymph node metastases by magnetic resonance imaging

Objectives: To evaluate the usefulness of magnetic resonance imaging in det ecting primary medullary thyroid carcinoma (MTC) and regional metastasis to the lymph nodes, and to correlate magnetic resonance signal intensity to p athologic changes. Materials and Methods: Magnetic resonance images in 14 patients with MTC (9 with primary disease, 5 with recurrent disease) were reviewed for signal i ntensities, tumor morphologic characteristics, and tumor invasion with spin -echo T-1-weighted images (T1WIs), T-2-weighted images (T2WIs), and gadolin ium-enhanced T1WIs. Multiple regression analysis was used to examine the co rrelation between T-2-weighted signal intensity and pathologic findings. Ly mph nodes were evaluated based on signal and morphologic characteristics. Results: Magnetic resonance imaging detected tumors in 9 (90%) of the 10 pa tients who had MTC in the thyroid gland. Extrathyroidal spread of the tumor s was correctly predicted using this procedure. Most tumors were hyperinten se or markedly hyperintense on T2WI. T-2-weighted signal intensity of the t umor was associated with increased amyloid deposition and high tumor cellul arity and low level of fibrosis (r=0.91, P=.01). Lymph node metastasis was present in 38 (23%) of 168 surgically dissected nodes. The combined use of 4 criteria (nodule size, a minimum-maximum diameter ratio of 0.80 or greate r, merited hyperintensity on T2WI, and necrosis in the node) yielded a high detection accuracy (93%) for nodal metastasis, with 74% sensitivity and 98 % specificity. Conclusions: Magnetic resonance imaging is useful for detecting primary and recurrent MTC, and its signal intensity reflects the underlying pathologic changes.