Localization of medullary thyroid carcinoma metastasis in a multiple endocrine neoplasia type 2A patient by 6-[18F]-fluorodopamine positron emission tomography.

6-[(18)F]fluorodopamine, a substrate for the norepinephrine transporter, has been used as a tumor-seeking tracer in positron emission tomography (PET) to localize pheochromocytomas and other chromaffin tumors. Here, we report the case of a 42-yr-old woman with multiple endocrine neoplasia type 2A, in whom biopsy-proven recurrent medullary thyroid cancer (MTC) was detected by 6-[(18)F]fluorodopamine PET scanning. The patient had previously undergone bilateral adrenalectomy for pheochromocytoma, total thyroidectomy, and extirpation of a parapharyngeal MTC metastatic deposit. An increase in plasma calcitonin 5 yr after her initial presentation was further investigated, leading to the discovery of a mass in the left parapharyngeal space. Levels of serum and urine catecholamines and metanephrines were normal. To exclude a hormonally silent pheochromocytoma metastasis, 6-[(18)F]fluorodopamine PET was performed. The study showed a focus of radionuclide accumulation corresponding to the parapharyngeal mass. After resection of the latter, pathology confirmed metastatic MTC. To our knowledge, this is the first case of metastatic, histologically proven MTC, which was unequivocally detected by 6-[(18)F]fluorodopamine PET scanning. Because norepinephrine transporter systems have been previously found in MTC, it is conceivable that 6-[(18)F]fluorodopamine PET scanning can be used for the diagnostic localization of this tumor and its metastatic deposits because total and early resection is beneficial to the outcome of the patient.