A retropharyngeal mass in a young boy.

Ayoungboywasnotedduring routineadenotonsillectomytohave a large firm mass in the posteriolateral pharyngeal wall and was referredtoatertiarymedicalcenter.Postoperatively,hedevelopedmild velopharyngeal insufficiency.Onflexibleendoscopy,theposteriorpharyngeal mass was clearly visible. Magnetic resonance imaging (MRI) oftheneckrevealeda3 × 2 × 1-cmfusiformlesionattachedtothemedial aspect of the left carotid space, extending to the midline retropharyngealspaceatthe levelofC2toC4(Figure,A).Themassshowed homogenous enhancementwith gadolinium contrast (not shown). The patient was taken to the operating room, and a transoral approach via horizontal incision in the level of orohypopharynx was performed. The firm encapsulated mass was easily identified and dissected free from surrounding tissue (Figure, B). The mass showed a narrow extension to the carotid space. On gross examination, the mass was firm and encapsulated. Hematoxylin-eosin–stained slides at low power (original magnification ×40) revealed a Schwannian-like background of eosinophilic, spindle-shaped cells (Figure, C). At higher power (original magnification ×100), clusters of well-differentiated ganglion cells with large round nuclei, prominent nucleoli, and granular basophilic Nissle substance (endoplasmic reticulum and ribosomes present in the cytoplasm of neural cells) were seen (Figure, D). Postoperatively, the patient was noted to have unilateral mild drooping of his eyelid, and his left pupil was constricted (yet responded to light) on the side of the resected lesion. Repeated MRI 6 months later showed no recurrence. What is your diagnosis? A B