A 19-year-old woman has noted swelling in the back of her mouth for 2 months. On dental examination, she has an area of swelling in the location of the left third molar. Dental radiographs show a radiolucent unilocular, well-circumscribed cyst surrounding the crown of the unerupted third mandibular molar. The lesion is excised, and on microscopic examination, the cyst is lined by stratified squamous epithelium and surrounded by a chronic inflammatory infiltrate. What is the most likely diagnosis?