Clinical application of 201Tl scintigraphy in patients with cold thyroid nodules.

201Tl-chloride scintigraphy was performed in 45 patients with cold thyroid nodules. The 201Tl scintigram was positive in 17 of 18 thyroid patients with cancer (94.4%), 8 of 20 patients with an ademoma (40.0%), 1 of 2 adenomatous goiter patients (50.0%), and all of 5 cases of chronic thyroiditis (100.0%). When the cold nodule was demonstrated to be positive with 201Tl, the statistical chance of the lesion being a cellular one was 100.0% and a risk of its malignancy was 54.8%. On the other hand, the nodule with negative 201Tl concentration had a 14.3% chance of cellularity and a 7.1% risk of malignancy. Thus, 201Tl scintigraphy is of use in the differential diagnosis of the cold thyroid nodule.