Intra-adenoidal retention cysts, also known as adenoidal retention cysts, mucous retention cysts of the nasopharynx or just intra-adenoid cysts, are a type of benign nasopharyngeal cystic lesions seen within the glandular structures of the nasopharynx 1-5.
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Terminology
Intra-adenoid cyst is a fairly generic term that includes several causes of cysts within the adenoidal tissue. Tornwaldt cysts, are distinct in their etiology, location, and histological structure of the cyst wall 1-4.
Epidemiology
Intra-adenoidal cysts have been reported in up to 6-10% of individuals 1-4. They have been described in all age groups with most being found in the 2nd to 6th decades of life 3.
Clinical presentation
Most intra-adenoid cysts are asymptomatic and discovered incidentally 1. Symptomatic cases can present with a variety of clinical features depending on the cyst location and size.
Complications
Complications include infection or also otitis media due to Eustachian tube obstruction 5.
Pathology
Intra-adenoidal retention cysts are typically characterized by grooved surfaces and squamous ciliated epithelium or columnar epithelium with residual lymphoid tissue and mucous 3-5. Most intra-adenoid cysts are rather small 3,5.
Etiology
They form due to the retraction of glandular tissue, from chronic inflammation 1 due to trapped mucus in the pharyngeal adenoid tissue or the mucosa 3.
Location
They are found in a parasagittal, or eccentric lateral location within the lymphoid tissue of the pharyngeal space and a small percentage in a median location 3 anterior to the pharyngobasilar fascia 1,5.
Radiographic features
Intra-adenoidal cysts are typically well-circumscribed, rounded to oblong sometimes lesions located within lymphoid tissue or the mucosa of the nasopharynx.
The size of these cysts can vary, ranging from 2-20 mm 1,5, but most are subcentimeter 3,5.
CT
These cysts may appear hypodense compared to surrounding tissue due to their fluid content 1.
MRI
MRI imaging of intra-adenoidal cysts typically shows well-circumscribed lesions with a thin wall and the signal characteristics of retention cysts 1.
T1: variable, typically hypointense
T2: typically hyperintense
T1 C+ (Gd): no enhancement 1,5
Treatment and prognosis
Intra-adenoid cysts might require treatment if they are symptomatic or in the setting of complications, such as infection or Eustachian tube obstruction 4,5. Surgical options include cyst drainage or complete excision depending on the cyst's characteristics and location 4,5.
Differential diagnosis
Lesions that look similar to conventional intra-adenoid cysts on imaging include the following entities 1:
abscess: thick rim enhancement
nasopharyngeal carcinoma: up to 12% are midline 2
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