Recurrent medullary carcinoma of the thyroid demonstrated by thallium-201 scintigraphy.

Thallium-201 scintigraphy has been used in the evaluation of thyroid neoplasms, but uptake in recurrent or persistent medullary thyroid cancer has not been reported. We present two cases where focal 201TI activity localized superior mediastinal recurrences which were subsequently resected. Postoperative 201TI scans in both cases showed elimination of the focal uptake seen before surgery, as well as return of previously elevated serum calcitonin levels to normal. Scanning with 201TI may be useful in the preoperative localization of recurrent medullary thyroid cancer.