[Persistence of the third branchial arch]. / Persistencia de tercer arco branquial.

The third branquial arch anomalies represent less than 1% of this deformites. The clinical manifestation can be varied althouth the formation of cysts is the commonest one and may appear at any time in life. We report the clinical case of a 7 year old boy with an neck mass. This mass was diagnosed as a branquial cyst. The patologist found a "timic reminescences". We carry out a review of the literature for this pathology.