Imaging description

Cystic mass lesions of the nasopharynx are common and often encountered incidentally on CTs and MRIs done for other reasons. The most common cystic masses seen in the nasopharynx are mucous retention cysts (MRC), which are often asymptomatic. MRC can occur anywhere in the upper aerodigestive system, but the nasopharynx is the most frequent site, followed by the valleculae. MRC wall has a pseudostratified ciliated epithelium and the cyst contains fluid that appears hypoattenuating on CT, hypointense on T1-weighted MRI, and markedly hyperintense on T2-weighted MRI, although cysts with a high protein content can demonstrate increased T1 and decreased T2 signal (Fig. 77.1) [1].

MRCs can be found anywhere in the nasopharynx but most commonly involve the lateral recesses and occasionally obstruct the Eustachian canals. They range from a few millimeters up to 20mm in size. MRCs are covered with intact mucosa on endoscopic exam and may only be appreciated if they create a bulge on the nasopharyngeal wall.