There is a well-defined lobulated cystic lesion arising from the posterior left maxillary alveolus and extending into the maxillary sinus. The walls are thin and smooth and there is no spiculation or periosteal reaction present. Superiorly the lesion is centred around the crown of the impacted and displaced 28, with its roots embedded in the lateral wall of the maxillary sinus. The tooth is intact. The lesion measures 31 x 35 x 29 mm (cc by AP by transverse). There is bony erosion of the lateral wall of the lesion and the soft tissue component abuts the medial border of the masseter and the anterior border of the temporalis and lateral pterygoid muscles but there is no evidence of muscle invasion. It also abuts but does not erode the anterior cortex of the mandibular ramus.
Left maxillary cystic lesion associated with the crown of the unerupted molar tooth (28) in keeping with an odontogenic keratocyst given the bony expansion. DDx include dentigerous cyst or ameloblastoma.