Iodine 131 uptake in a bronchogenic cyst in a patient with differentiated thyroid carcinoma

BACKGROUND: After thyroidectomy for differentiated thyroid carcinoma, extra cervical uptake of iodine 131 is suggestive of metastasic dissemination. Fa lse positives can however occur. CASE REPORT: Differentiated thryoid carcinoma was found in a female patient with a non-functional nodule. Two years after subtotal thyroidectomy and a n ablative dose of iodine 131, the whole body scan showed abdominal mediast inal uptake with low serum 'thyroglobulin level. Considering the possibilit y of tumor recurrence or lymph node metastasis, the mass was excised. The h istology diagnosis was mediastinal bronchogenic cyst DISUCUSSION: To date, iodine uptake in a bronchogenic cyst has not been rep orted among other false-positives previously described. The pathophysiology of this iodine 131 uptake in a bronchogenic cyst is still unknown: the pre sence of NIS symporter or a protein which can organify iodine in the mucus cells of the cyst remains to be proven.