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Abstract

Unusual features of 131I uptake during thyroid cancer scintigraphy may lead to a false-positive diagnosis of residual or recurrent malignancy and associated metastasis. A proper understanding of the causes of falsepositive 131I scans is essential for accurate interpretationof the images and to obviate diagnostic errors which may leadto administration of unnecessary therapy doses. We are reporting a case of a 55-years old man with history of total thyroidectomy for papillary thyroid cancer, followed by ablation therapy with 100 mCi of 131I for residual thyroid disease. A follow-up scan obtained after one year showed a large area of 131I uptake in mediastinum, which was subsequently found to be due to accumulationof radioiodine in a grossly dilated esophagus secondary toachalasia. Â For the accurate interpretation of 131I whole-body scans, awareness of potential causes of false positive findings is important to ovoid unnecessary radiation burden to the patients.