[Cysts and pseudocysts of the parotid]

Parotid gland are subdivided in malformative dysgenetic cysts and in acquired cysts. Among malformative cysts, lymphoepithelial cysts so-called branchial cysts are the most frequent. Histologically the cystic cavity is lined by squamous epithelium with various amounts of underlying lymphoid tissue. Other varieties of malformative cysts are exceptional: cystic teratomas with several sorts of adult tissues, polycystic parotid gland and congenital ductal ectasia. Acquired cysts are another important group: retention cysts are found in adult and old people. Microscopically these cysts are lined by a single or pseudostratified epithelium rested on a layer of connective tissue without any lymphoid tissue. Lymphoid cystic hyperplasia arising in HIV infection can be included in this group of acquired cysts. Finally these parotid cysts have to be differentiated from pseudocysts without an epithelial lining and from cystic tumors as cystadenolymphoma and cystic mucoepidermoid carcinoma.