18F-FDG PET/CT of Papillary Carcinoma in a Lateral Thyroglossal Duct Cyst.

A 69-year-old man presented with bulging of the right oropharyngeal wall, which revealed cytopathologically malignant cells. The man underwent MRI and F-FDG PET/CT, which demonstrated a cystic parapharyngeal lesion with an F-FDG-avid soft tissue component and right cervical lymph node. The patient was operated on and showed thyroid cancer in normal thyroid tissue, compatible with a papillary thyroid carcinoma in a lateral thyroglossal duct cyst and 2 ipsilateral lymph node metastases. Despite its rarity, papillary thyroid carcinoma in a thyroglossal duct cyst should be kept as one of the differential diagnoses in patients presenting with parapharyngeal cystic lesion.