Luminal, Intramural Unicystic Ameloblastoma with Marked Fluid-Fluid Level: Validity of CT and MRI Findings.

We report herein a case of a luminal and intramural unicystic ameloblastoma (UA) with a marked fluid-fluid level. The validity of imaging findings in diagnosing UA in the present case is discussed in reference to the literature. The patient was a 50-year-old woman who presented with swelling of the gingiva in the region of the left mandibular third molar and numbness in the lower lip. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a large mass lesion with a unilocular appearance and a biphasic aspect, suggesting liquid content. Contrast-enhanced MRI (CE-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) demonstrated that the biphasic aspect indicated a fluid-fluid level with no blood pooling/flow; it also revealed a thick rim-enhanced margin with mural protrusion. Postoperatively, the lesion was histopathologically diagnosed as a luminal and intramural UA. In conclusion, extensive imaging including both standard CT and MRI together with CE-MRI and DCE-MRI allowed mural protrusions or nodules on a thick cystic wall and liquid content to be correctly identified. This suggests that such imaging can play an important role in diagnosing a UA, even though the results were at first misleading due to the marked fluid-fluid level.