A possible inflammatory reaction in a lateral neck cyst (branchial cyst) because of odontogenic infection.

We present the case of a woman who suffered from an acutely infected diffuse mass in the right neck. This mass had grown rapidly after difficult extraction of a tooth. Histologic analysis of the excised material revealed a lateral neck cyst with a lymph node that showed signs of an acute inflammation near the cyst. These findings support the theory that a preexisting lateral neck cyst may be "activated" by an intraoral inflammation. The different theories of the origin of lateral neck cysts are presented and discussed in the context of the case description.