67Ga-Citrate and the Nonfunctioning Thyroid Nodule

Nineteen patients identified by 125I, 131I, or 99mTc-pertechnetate imaging as harboring a solitary “cold nodule” of the thyroid gland were evaluated further by 67Ga-citrate thyroid scans. Histologic examination of the thyroid tumors was performed in all cases. Of the seven thyroid tumors shown to be malignant, only three selectively concentrated 67Ga-citrate. Two of these were anaplastic carcinoma; the third was a mixed papillary-follicular carcinoma containing multiple foci of poorly differentiated cells. None of the 12 benign nodules in this investigation concentrated 67Ga-citrate. These included follicular adenomas and colloid nodules. No cases of subacute or chronic lymphocytic thyroiditis were encountered. Our results indicate that although 67Ga-citrate may be of value in identifying anaplastic thyroid tumors, it has limited application in the diagnosis of solitary cold nodules.