Hashimoto's disease presenting as an unusual retropharyngeal mass

The case of a 57-year-old male with a large and rapidly growing mass in the retropharyngeal space is presented. Whilst this lesion had many of the features of malignancy, histopathological examination has shown it to be due to Hashimoto's thyroiditis, which appears to have developed in ectopic thyroid remnants. A rapid and sustained resolution of the mass has followed conventional therapy.