Nasopharyngeal Retention Cyst

These images demonstrate a well-circumscribed submucosal hypodense cystic lesion in the right nasopharynx which is to the right of midline in a preadolescent child with prominent, but age-appropriate adenoids. Hounsfield unit interrogation shows that it is not simple fluid or soft tissue density. The differential considerations include a mucous retention cyst, Tornwaldt cyst, or adenoidal abscess. This patient was scanned for head trauma so infection is unlikely. Given that it was off midline the best diagnosis is retention cyst of the nasopharynx, likely in the lateral pharyngeal recess. If it was midline, the leading differential would be a Tornwaldt cyst (cyst of notochordal remnant).