Lymphoproliferative disorders of the thyroid gland: radiological appearances.

Images of lymphoproliferative disorders of the thyroid by ultrasonography (US), computed tomography (CT), Tc(m)-99 and Ga-67 scintigraphy were analysed in eight patients (two men and six women, aged 42-83 years). Seven patients were diagnosed as having primary lymphoma and one plasmacytoma. Ultrasound revealed a solid mass with homogeneous and very low echogenicity clearly distinguishable from residual thyroid tissue in five patients, diffuse hypoechoic goitre in one and multiple irregular hypoechoic nodules in both lobes in the patient with plasmacytoma (Case 8). Computed tomography demonstrated a focal low-density area in six cases of lymphoma and decreased density throughout the gland in the other two patients. Tc(m)-99 scintigraphy showed hemilobar enlargement with decreased and uneven trapping, cold area or complete lobar defect in six patients with lymphoma and no trapping in the case of plasmacytoma. Ga-67 scintigraphy demonstrated high accumulation in lymphoma and faint accumulation in the case of plasmacytoma. Radiological manifestations with a focal lesion were considered typical and diagnostic of primary thyroid lymphoma, while in one case with diffuse infiltration through the whole gland, the differential diagnosis from Hashimoto's thyroiditis could not be made. In the final case, cells infiltrated diffusely to form islands with patchy distribution among well preserved follicles, correlating with the multiple hypoechoic areas observed by US.