Hypopharyngeal retention cyst is a benign cystic lesion resulting from obstruction of the ducts of minor salivary glands (seromucinous glands) in the pharyngeal and laryngeal mucosa. It most commonly occurs in the vallecula (between tongue base and epiglottis), epiglottic surface (lingual or laryngeal), piriform sinus, and aryepiglottic folds. On radiological imaging, it appears as a smooth-bordered, non-enhancing, fluid-density (CT) or T2 hyperintense (MRI) cystic lesion. Incidental detection rate is high; most have no clinical significance. However, large vallecular cysts can cause airway obstruction in neonates and infants — potentially requiring emergent intubation and surgical intervention.
Age Range
20-80
Peak Age
50
Gender
Equal
Prevalence
Common
Retention cysts result from duct obstruction of minor salivary glands (seromucinous glands) widely present in the pharyngeal and laryngeal mucosa. These glands continuously produce fluid (serous and mucinous secretions); duct obstruction (chronic inflammation, trauma, prior surgery/intubation) prevents drainage and secretions accumulate in the gland lumen. Increasing intraluminal pressure leads to cyst formation. The cyst wall is lined by glandular epithelium (gland duct epithelium) — this feature distinguishes retention cysts from other cyst types (epidermoid, dermoid, branchial). Cyst content is clear serous or gel-consistency mucinous fluid; low density on CT (0-20 HU) and high T2 signal on MRI reflect this fluid content. The cyst wall contains thin fibrous tissue and is not vascularized — no enhancement is expected. Cysts grow slowly and do not invade surrounding tissues; large cysts can mechanically displace adjacent structures. Vallecular cysts are particularly dangerous in neonates because the infant airway is small and even a small cyst can cause significant obstruction. In adults, most cysts are incidental and of no clinical significance.
A smooth-bordered, non-enhancing, markedly T2 hyperintense cystic lesion in the vallecula or epiglottis is the signature finding of retention cyst. Absence of DWI restriction excludes epidermoid cyst, and absence of enhancement excludes solid tumors.
Non-contrast CT shows a smooth-bordered, round/oval, fluid-density (0-20 HU) hypodense cystic lesion in the vallecula, epiglottis, or piriform sinus. The cyst wall is thin without distinct wall thickening. No internal septation, calcification, or solid component is present. Surrounding mucosa and bony structures are normal — no invasion or destruction is expected. On contrast-enhanced series, the cyst shows no enhancement; even thin rim enhancement is absent (if not infected).
Report Sentence
A smooth-bordered, non-enhancing, fluid-density cystic lesion is noted in the left vallecula, consistent with a retention cyst; assessed as an incidental finding.
On MRI T2-weighted sequences, the retention cyst shows markedly hyperintense (bright) signal — clearly separated from surrounding soft tissue due to fluid content. The cyst shows homogeneous signal; no internal septation or solid component. The cyst wall may be seen as a thin low-signal line on T2. On T1, the cyst is usually hypointense (serous fluid); proteinaceous fluid may show mild T1 hyperintensity. No enhancement is present. No diffusion restriction is expected on DWI — this feature distinguishes from epidermoid cyst.
Report Sentence
A cystic lesion markedly hyperintense on T2, hypointense on T1, with no enhancement or DWI restriction is noted on the lingual surface of the epiglottis, consistent with a retention cyst.
On transcervical or intraoral US, the retention cyst appears as an anechoic, smooth-bordered cystic lesion. It shows posterior acoustic enhancement — a characteristic US finding of cystic structures. No internal echogenicity, solid component, or septa are present. No vascularity is detected on Doppler. US is particularly useful in evaluating vallecular and epiglottic cysts.
Report Sentence
On transcervical US, an anechoic, smooth-bordered cystic lesion is noted in the vallecula region with posterior acoustic enhancement; consistent with a retention cyst.
Retention cyst shows no diffusion restriction on DWI — ADC values are in the high range consistent with free water (>2.0×10⁻³ mm²/s). This feature distinguishes from epidermoid cyst; epidermoid cysts show diffusion restriction and high signal on DWI due to keratin debris. DWI differentiation is particularly clinically important for cysts located in the vallecula and epiglottis.
Report Sentence
The cystic lesion shows no diffusion restriction on DWI with ADC values in the high range; epidermoid cyst has been excluded, consistent with retention cyst.
Criteria
Located in the vallecula (between tongue base and epiglottis)
Distinct Features
Most common location; airway obstruction risk in neonates; usually incidental in adults
Criteria
Located on epiglottic surface (lingual or laryngeal)
Distinct Features
On laryngeal surface may narrow airway; on lingual surface usually asymptomatic
Criteria
Located in the piriform sinus
Distinct Features
May cause dysphagia symptoms; differential diagnosis with SCC is important
Distinguishing Feature
SCC solid mass, heterogeneous enhancement, invasive margins; cyst non-enhancing fluid lesion, smooth borders
Distinguishing Feature
Zenker retropharyngeal air-fluid level, connected to posterior wall; retention cyst intraluminal, no air content
Distinguishing Feature
Abscess rim enhancement, fever, acute presentation; cyst no enhancement, asymptomatic
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upHypopharyngeal retention cysts are usually incidental findings requiring no treatment. Symptomatic cysts (dysphagia, globus sensation) are treated with endoscopic marsupialization. In neonates, large vallecular cysts may require EMERGENT airway intervention — pediatric ENT consultation is mandatory.
Hypopharyngeal retention cysts are usually incidental findings requiring no treatment. Large vallecular cysts can cause airway obstruction in neonates (neonatal stridor). In adults, symptomatic cysts are treated with endoscopic marsupialization.