It is defined as cysts lined by epithelium with underlying stroma showing dense lymphoid aggregates
It can be associated with HIV infection
Clinical features
Site: presents in parotid or upper cervical lymph nodes
Age: Most common in adults (peak age is from 2nd to 4th decade) but can occur in children also
Sex: male predominance with male to female ratio of 7:1
Clinical presentation: presents as firm compressible swelling which is unilateral and usually unicystic
If associated with HIV – presents as bilateral parotid swelling accompanied by cervical lymphadenopathy
Etiopathogenesis
Few theories have been proposed regarding its origin
Originates from remnants of embryonic branchial apparatus, similar to a branchial cleft cyst
Another theory is that they develop from cystic proliferation of salivary gland epithelium which is entrapped in intraparotid and paraparotid lymphnodes
It can be lymphocytic response to cyst as in reactive tumor associated lymphoid tissue that proliferates in salivary gland neoplasms
Morphology
Gross
Uniloculated or multiloculated cyst (If associated with HIV)
Solid, tan homogenous areas of the cyst wall and granular areas projecting into cyst lumen represent lymphoid tissue
Microscopy
Lymphoepithelial cysts have more irregular or undulating luminal surface when compared to salivary duct cyst
Cyst wall is usually lined by squamous epithelium
Other epithelium which can be seen are
Cuboidal epithelium
Columnar epithelium with goblet like cells
Pseudostratified ciliated columnar epithelium
Beneath the epithelium, stroma shows dense lymphoid tissue with lymphoid follicles.
Lymphocytes may infiltrate epithelium.
Lymphoid tissue is well demarcated from surrounding salivary gland parenchyma
Sebaceous cells can be rarely seen in the wall
Differential diagnosis
Warthin tumor – Cystic spaces with papillae lined by double layered epithelium i,e. tall-columnar cell which are oncocytic and basal layer. Lymphoid follicles are seen in stroma
Salivary duct cyst: lined by stratified squamous epithelium. Goblet type mucinous or oncocytic cells may be present in epithelium. Stroma shows atrophic acini and chronic inflammatory cells
Mucocele – mucinous material in cyst and fibrotic cyst wall is lined by cuboidal to stratified squamous epithelium.
Polycystic disease of parotid – small epithelial cyst interspersed through out