A 16 year old girl came in with a recurrent swelling of the right maxilla. She had surgery several years ago. She arrived with a CT which is unusual. We took a picture of the CT and emailed it to my friend and radiologist John Melvin in the USA. His report: "expansile lesion of the maxilla which may be originating in the area of a tooth root.  The bone appears expanded and remodeled (rather than destroyed) suggesting a relatively slowly growing mass. The first thing that comes to my mind is a dentigerous cyst or periapical cyst with ameloblastoma being my next choice.  Dr. Melvin was correct. We explored her maxilla and found an ectopic tooth with a dentigerous cyst. There was a molar tooth in the lateral aspect of the maxillary wall. We removed the tooth and she recovered without problems. 

CT of maxilla (note image is reversed

Molar tooth in superior, lateral aspect of sinus

Ectopic molar