Misinterpretation of iodine uptake in papillary thyroid carcinoma and primary lung adenocarcinoma.

This is the first case report of an iodine-storing metastasising carcinoma of extrathyroidal origin and the simultaneous presence of a papillary thyroid carcinoma. In the course of the disease, an increase in pathological iodine uptake was observed after repeated iodine-131 ablation, so that the original tentative diagnosis of a metastasising, differentiated thyroid carcinoma appeared to be confirmed; moreover, the histological work-up of a femur metastasis--without adequate immunohistochemical assessment--was misinterpreted. What is also remarkable about this case report is a pathological iodine-131 uptake both in the extrathyroidal primary tumor and the metastases.