FALSE-POSITIVE I-131 WHOLE-BODY SCANS DUE TO CHOLECYSTITIS AND SEBACEOUS CYST

False-positive whole-body I-131 scans are not frequent but have seriou s consequences in the management of patients with thyroid cancer. They can be classified in four main groups: elimination of iodine in body fluids, infection or inflammation, cysts or transudates and nonthyroid tumors. We report on two patients with false-positive post-therapy I- 131 scans. The first patient had uptake projected in the right pelvic area which was later proven to be a large gluteal sebaceous cyst. The second patient had uptake in the gallbladder area that did not disappe ar after I-131 treatment; she underwent exploratory laparotomy which r evealed extensive chronic cholecystitis. These cases illustrate two ne w causes of false-positive I-131 whole-body scans (sebaceous cyst and cholecystitis), which highlights two mechanisms (elimination in body f luid and inflammation).