[Rare cervicofacial cysts and fistulas in children].

Among the various congenital cervicofacial swellings observed in children, three types are rarely encountered in general practice: auriculobranchial cysts and fistulae, thymic cysts and cystic lymphangiomas. To resolve diagnostic and therapeutic problems related to these rare lesions it is essential that their etiopathogenic bases be understood. Auriculobranchial cysts and fistulae present clinical symptoms (cervical, parotid, auricular) that are only poorly evidenced and are related mainly to infection. Surgical excision requires a wide approach route of the parotidectomy type with preliminary isolation of the facial nerve. Thymic cysts result from embryogenic anomalies leading to remnants from the 3rd endobranchial pouch and/or degenerative disorders of Hassal's corpuscles. Of mainly perioperative detection their exeresis requires investigation of possible inferior mediastinal prolongations and preservation of healthy thymic parenchyma. Cystic lymphangiomas arise from dysembryoplasia of the lymphatic system, two opposing pathogenic theories existing to explain their origin. They are serious lesions because of their dissecting tendencies and their inexorable growth in the vast majority of cases. Two forms of lymphangioma, from the embryologic, diagnostic and therapeutic points of view, can be distinguished: those of extraparotid origin and those developing from the parotid.