Findings:
There is a well-defined expansile 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. Laterally the lesion is centred around the impacted and displaced tooth 26, with its roots partially embedded in the lateral wall of the maxillary sinus. The tooth is intact.
Hyperdense material is also noted overlying the posterolateral wall of the left maxillary sinus, likely in keeping with dysplastic 2nd molar.
The lesion measures 53 x 36 x 43 mm (cc by AP by transverse). There is bony erosion of the lateral and anterior wall of the lesion and some soft tissue component abutting the anteromedial border of the masseter but there is no evidence of muscle invasion. It also abuts but does not erode the anterior cortex of the mandibular ramus.
The medial wall of the left maxillary sinus protrudes into the left nasal cavity, displacing the left inferior nasal turbinate medially. Concha bullosa is seen on the left.
Mucosal thickening thickening is seen in a few ethmoid air cells on the right. Small osteomas are seen in frontal sinuses bilaterally and in one posterior ethmoid air cell on the right.
The orbits are unremarkable. The mastoid air cells and the middle ear cavities are clear.
No lymphadenopathy.
Impression:
Left maxillary cystic lesion associated with the crown of the unerupted molar tooth, likely in keeping with an odontogenic keratocyst given the bony expansion. DDx include dentigerous cyst or ameloblastoma.