Ectopic Gastric Mucosa with Intense Iodine Uptake in the Esophagus Mimicking Thoracic Metastasis - A Case Report

Objectives We report a case of Ectopic Gastric Mucosa with Intense Iodine Uptake in the Esophagus Mimicking Thoracic Metastasis

Methods Case Report

Results Thyroid cancer is the most common endocrine cancer (1.0-1.5% of all new cancers in the USA). Iodine-131 (I-131) whole-body scan (WBS) plays an important role in the management of patients with differentiated thyroid carcinoma (DTC), to detect normal thyroid remnants and recurrent or metastatic disease. A focus of I-131 accumulation outside the thyroid bed and out of the areas of physiological uptake are strongly suggestive of metastasis. However, many false-positive findings have been reported in the literature. MBC, 46 year old male, underwent total thyroidectomy for DTC which revealed papillary carcinoma in the right lobe, with 1,8 cm and extensive invasion of the capsule of the thyroid gland, but with only focal extra glandular involvement. One out of 5 lymphnodes removed was metastatic. He performed staging with lab, ultrasound and a WBS with I-131. The thyroglobulin (Tg) level was 2.2 ng/ ml, negative antibodies, TSH: 6.8 (not yet on complete suppression), negative ultrasound, but the WBS shown an intense uptake on the midthorax. A therapeutic dose of 150 mCi was administered under recombinant human TSH, with peak Tg of 13.3, which fell to 0 post iodine. On the WBS post treatment besides the uptake in the thyroid bed, the same image in midthorax was seen. At this time we performed a SPECT with CT fusion imaging, which showed that the area was located in the esophagus. An endoscopy found out the presence of an atypical tissue that was biopsied and revealed ectopic gastric mucosa (EGM). EGM of the esophagus is uncommon with endoscopic studies reporting a prevalence ranging from 1-18%. The causes of iodine uptake in EGM are functional NIS expression in gastrointestinal tract and retention of I-131 in mucosal secretions, associated with or without structural changes. In this reported case, we show a patient with low Tg with a persistent focal iodine uptake in midthorax. According to current practice, the observation of I-131 uptake suggestive of metastasis of a DTC must be evaluated together with a clinical scenario, which involves high Tg serum levels, an anatomic altered imaging and a history that would favor metastatic cancer. An isolated I-131 uptake is unlikely to be a metastasis, but rather a false-positive finding as shown in the present case. Using advanced hybrid imaging in nuclear medicine might help to solve the issue.

Conclusions We report a case that shows that performing hybrid imaging and evaluating the clinical context can avoid false-positive findings in the iodine whole body imaging.