MR imaging of primary leiomyosarcoma of the thyroid gland

Primary leiomyosarcoma of the thyroid gland is extremely rare and radiologi cal information on this tumor is scant. We presented radiological findings on primary thyroid leiomyosarcoma in a 66-year-old woman in which anaplasti c carcinoma was suspected based on clinical and cytological features and di scussed the radiological clues to distinguish between the two diseases. Ult rasonography showed an ill-defined hypoechoic mass without halo in the left lobe and the isthmus of the thyroid gland. Computed tomography depicted a low-density mass with calcification and necrosis, which invaded the thyroid cartilage. No lymphadenopathy was seen. The tumor was demonstrated as an i sointense mass on T1-weighted MR images and a mass of intermediate signal o n T2-weighted images. The tumor showed a fair enhancement on gadolinium-enh anced T1-weighted images. Although the radiological picture was nonspecific , primary thyroid leiomyosarcoma appeared less invasive and far less freque nt in developing nodal metastasis than anaplastic carcinoma in light of the literature. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.