FALSE-POSITIVE RADIOIODINE WHOLE-BODY SCAN IN THYROID-CANCER PATIENTSDUE TO UNRELATED PATHOLOGY

Radioiodine whole-body scanning is the imaging modality of the highest accuracy in diagnosing metastases from differentiated thyroid cancer. However, unrelated pathology in one of several nonthyroidal tissues t hat normally take-up/secrete radioiodine may result in a false positiv e scan. The authors report cases of an ectopic kidney, chronic sinusit is, dacryocystitis, and an artificial eye, complicating differentiated thyroid cancer, that on radioiodine scanning mimicked lumbar, frontal , and left and right orbital bone metastases, respectively. The nature of the radioiodine uptake was suspected from the results of a bone sc an and proven by ultrasound (ectopic kidney), by reimaging after speci fic treatment (chronic sinusitis, and dacryocystitis), or by post-wash ing reimaging (artificial eye). To our knowledge, this is the first re port of such cases. Nonthyroidal pathology should be excluded before e xposing patients with apparent thyroid cancer metastases that have aty pical characteristics on radioiodine whole body imaging.