Submandibular Ectopic Thymic Mass in a 6-Month-Old Infant

Infant ectopic cervical thymus is a relatively uncommon diagnosis and, in many cases, subclinical. If not subclinical, it may present as a palpable swelling or with compressive symptoms (i.e., stridor or dysphagia). Standard radiologic workup includes an ultrasound followed by magnetic resonance imaging (MRI) with tissue sampling if the ultrasound is indeterminate. In this case, an incidental submandibular mass was noted on a noncontrast MRI for seizures in a 6-month-old male infant. A radiologic and pathologic workup was performed for evaluation. However, this case is unique as fluorodeoxyglucose positron emission tomography/computed tomography was also utilized to potentially aid in the establishment of a diagnosis.