Benign cystic mesothelioma: false-positive iodine accumulation in a patient with oncocytic follicular thyroid carcinoma.

Whole-body (131I) scintigraphy (WBS) is used to detect residual or metastatic tissue during treatment of differentiated thyroid carcinoma in combination with thyroglobulin (Tg) and ultrasonography of the neck. It is a highly sensitive method, but there is a high rate of false positives. We report the case of a 52-year-old woman with false-positive iodine accumulation in a benign cystic mesothelioma discovered during treatment for a oncocytic follicular thyroid carcinoma (stage pT2 pNx Mx). This lesion was detected by WBS and confirmed by surgery and histopathologic analysis.