False-Positive Whole-Body I-131 Scan In Thyroid Carcinoma Caused By Gastrooesophageal Reflux Disease

摘要

Many false-positive findings on I-131 scans have been reported. Recognition of them may avoid unnecessary repeated therapeutic doses of radioactive iodine. The authors describe a false positive cervical and mediastinal radioiodine uptake due to gastro oesophageal reflux disease in a 63 yr-old man with papillary thyroid cancer. Trough this case report, causes of such scintigraphic features are reviewed. Introduction Thyroid cancer is an hormono - dependent neoplasm, radio sensible in its differentiated shapes. After surgical ablation of the primitive tumor, radio iodine completes this treatment in case of cervical remnant or extra nodal metastases. Whole body 131 I scintigraphy has aided the follow up of differentiated thyroid cancer for several decades. However, this strong tool based on the presence of the sodium iodide symporter (NIS) in the basolateral surface of thyroid follicular cells is not perfect. A wide spectrum of potentially misleading artefacts can arise in 131 I whole body scans from various anatomical variants and physiological processes as well as several unrelated non-thyroidal disease processes [1]. Recognition of potential false-positive iodine-131 scans is critical to avoid the unnecessary exposure to further radiation from repeated therapeutic doses of radioactive iodine. Here, we describe a case of false positive whole body scan due to a gastro-oesophageal motility disorder. Case Report A 63-yr-old man with a long past of type 2 diabetes (25 years) and more recently a Parkinson disease (5 years), received ten years ago 3, 7 GBq of 131 I for post surgical ablation of residual cervical cells of a papillary carcinoma of the thyroid. Six months later, serum thyroglobulin test and whole body 131 I scan were negative. The patient was considered free of disease and the same results were shown on serum tests and scintigraphic follow-up for the last decade. Recently, a whole body scan performed two days after oral administration of 167 MBq of 131 I showed tree foci in the upper side of the neck and a linear mediastinal uptake. Patient interrogation revealed heartburn and acid regurgitation. He was effectively treated for gastro oesophageal reflux disease.A repeat scan after eating was negative. Serum thyroglobulin level was under 0,1 ng/ml. So we attributed the scintigraphic abnormalities to the gastrooesophageal reflux disease.