BREAST CYST SIMULATING METASTASES ON I-131 IMAGING IN THYROID-CARCINOMA

False-positive radioiodine uptake has been reported in many organ syst ems. We describe a female patient who had mixed papillary and follicul ar thyroid carcinoma, and on radioiodine total-body imaging demonstrat ed focal, lower-right chest uptake. Special prone imaging with the rig ht breast dependent proved that the uptake was inside the right breast . Review of a recent breast ultrasound and mammograms showed this upta ke to correspond to a large breast cyst. It is known that I-131 breast uptake may be functional within the mammary gland. In this patient, i t was due to retention within the cyst after the background activity d ecreased. Knowledge of this phenomenon may improve the interpretation of total-body (INa)-I-131 studies.