Incidental diagnosis of ectopic thyroid in the work-up of metastatic esophageal cancer: a case report

Ectopic thyroid occurs when the medial descent of the thyroid gland takes place inappropriately. Flurodeoxyglucose (FDG) uptake on the normal thyroid gland is rare. Etiologies for the FDG uptake include infection, inflammation, and malignancy. We report a rare case of ectopic thyroid which was suspected as metastatic lymph node on positron emission tomography-computerized tomography (PET-CT) scan during staging of esophageal adenocarcinoma. A 76-year-old man with no past notable chronic diseases was diagnosed with adenocarcinoma at the gastroesophageal (GE) junction. He was referred to the oncologist, who ordered FDG-PET-CT scan for the staging of cancer. On PET-CT scan, hypermetabolic focus measuring 2.2×2.1 cm with SUVmax 3.4 was present in the left supraclavicular region, which raised concerns for the metastatic disease to the lymph node. Fine-needle aspiration via ultrasound-guided approach was utilized to obtain biopsy, which resulted as benign thyroid tissue. To verify, repeat core biopsy was taken via CT-guided approach, the pathology again confirms benign thyroid tissue. No further intervention was proceeded on the ectopic thyroid. While past studies had shown FDG activity on thyroid lesions, prevalence of malignancy in these thyroid lesions is unclear. There is also no clear correlation between malignancy and SUVmax value. Therefore, we propose further studies are needed to understand the relationship between FDG uptake and thyroid lesions as well as to determine the follow-up algorithm for benign FDG avid lesions.