CT post-contrast CT post-contrast CT bone windows

Diagnosis: Dentigerous cyst

Dentigerous cyst are a subset of follicular cysts making up 95% of that group. The other 5% of follicular cysts are termed primordial cysts. Follicular cysts are part of the overall heading of odontogenic cysts which include follicular cysts, periodontal cysts, odontogenic karatocysts, and calcifying odontogenic cysts.

Dentigerous cysts tend to occur in young adulthood and arise in unerupted teeth. The cyst may become large and multilocular with a tooth being present within the cyst. The most common teeth involved are the mandibular 3rd molars and the maxillary canine teeth. When the dentigerous cyst is small, it may be distinguished from a normal dental follicle if it is larger than 2 cm in width. In that case, the unerupted tooth will most likely become a dentigerous cyst.

Ameloblastoma is a complication of a dentigerous cyst in 17% of cases and becomes less common as patients age beyond 30. Ameloblastoma is a cystic, epithelial neoplasm which is usually histologically benign but may rarely metastasize. On imaging, they may resemble dentigerous cyst but with more of a soft tissue component. In this case, the preoperative diagnosis was ameloblastoma due to the presence of the nodule soft tissue within the cyst however at pathology the diagnosis was dentigerous cyst. Other entities to consider in the differential of a cystic expansile lesion involving the maxillary sinus may include maxillary mucocele and aneurysmal bone cyst.

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Minami M, Kaneda T, Yamaoto H, et al. Ameloblastoma in the maxillomandibular region: MR imaging. Radiology, Aug 1992; 184(2):p389-93.