SECTION EDITOR: C. DOUGLAS PHILLIPS, MD
Diagnosis: Unicystic ameloblastoma (UA)
An ameloblastoma is a common odontogenic epithelial tumor that arises from cell rests of the dental lamina.1 It is the second most common odontogenic tumor and typically occurs in the jaws, with a predilection for the posterior region of the mandible; however, 15% to 20% of ameloblastomas are found in the maxillary sinus and are therefore not so rare. Although ameloblastomas are benign, they are destructive, locally invasive tumors, with a high rate of recurrence despite adequate surgical removal.2 According to the 2005 World Health Organization classification of odontogenic tumors, the variants of ameloblastomas are solid/multicystic, extraosseous, desmoplastic, and unicystic.3 Compared with the other variants, UA has a less aggressive nature and a lower recurrence rate.4 An ameloblastoma shows a predilection for intermediate signal intensity on T1-weighted MRIs, high signal intensity on T2-weighted MRIs, and avid enhancement only in the solid portion. By analyzing the signal intensity of MRIs, we can often distinguish the solid and cystic portions of the lesion. These types of ameloblastoma can be differentiated easily from other odontogenic cystic lesions. On the other hand, unilocular cystic-type ameloblastomas show nonspecific cysticlike signal intensity on T1- and T2-weighted MRIs. Therefore, it is difficult to distinguish UAs from other odontogenic cystic lesions such as dentigerous or radicular cysts with the use of MRI signal intensity alone. Recently, dynamic contrast-enhanced MRIs have been shown to be able to distinguish UAs from other cystic lesions by demonstrating thicker rim enhancement.5
Radiology Quiz Case 1: Diagnosis. Arch Otolaryngol Head Neck Surg. 2012;138(10):974. doi:10.1001/archotol.138.10.974
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