Focal Radioiodine Uptake in the Lower Limb: A Benign Mimicker of Metastasis in High-risk Differentiated Thyroid Cancer.

A 55-year-old man with high-risk papillary thyroid cancer underwent a second round of radioiodine therapy due to lung and lymph node metastases. A follow-up whole-body scan showed a new focal area of radioiodine uptake in the right lower limb, which was absent in previous scan and remained despite skin decontamination. Upon examination, a posttraumatic scab was found on the right leg from a fall 5 days prior. SPECT/CT imaging and scab healing during follow-up effectively ruled out bone and skin metastases. This case underscores the need to recognize false-positive radioiodine uptake in differentiated thyroid cancer for improved diagnostic accuracy and patient care.