[The branchiogenic cyst in the oncologic context].

8 patients with cystic carcinoma resembling a lateral cervical cyst by morphology and topography are reported. In 4 cases an analogous carcinoma later appeared in the ipsilateral tonsil, and in 2 tonsillectomized patients subsequent carcinoma developed in the palatopharyngeal arch or at the base of the tongue respectively. One carcinomatous cyst with consecutive involvement of the base of the tongue was preceded by a regular branchiogenic cyst on the opposite side. Removal of a recurrent branchiogenic cyst in another patient revealed unsuspected chronic myeloic leukaemia infiltrating adjacent lymph nodes. The hypotheses regarding the branchiogenic and lymphogenic pathogenesis of such carcinomatous cysts are discussed. Diagnosis should be elaborated as in any carcinomatous lump of the neck and should include serial sectioning of the tonsils and imaging of deep layers. The possibility of synchronous or metachronous tonsillar involvement must always be taken into consideration.