Scintigraphic detection of recurrence of medullary thyroid cancer

A case of recurrent medullary thyroid cancer (MTC) was evaluated with 123I-MIBG, 99mTc(V)-dimercaptosuccinic acid (DMSA), and 201Tl scintigraphy. This patient had been operated on for MTC in the right thyroid. Recently a left neck mass was noticed, and was suspected of being a recurrence of MTC based on increased plasma calcitonin (CT) and carcinoembryonic antigen (CEA). He was operated on for the neck mass which revealed MTC, and papillary thyroid cancer was incidentally found in the left thyroid, but the CT and CEA levels remained high, and remaining MTC tumor was suspected. But the location of the tumor was unknown. Although 99mTc(V)-DMSA scintigraphy is generally believed to be superior in sensitivity to 123I-MIBG scintigraphy, it did not demonstrate the tumor site but 201Tl and 123I-MIBG did. Furthermore, 123I-MIBG scintigraphy has greater specificity for tumors which arise in the neural crest. Judging from the results of this case and cases reported in the literatures, both 123I-MIBG and 99mTc(V)-DMSA should be performed in the detection of recurrent MTC.