Coexistence of a pseudolesion and a true lesion in the same location: a rare misleading imaging finding.

Congenital cholesteatoma and asymmetric fatty marrow are both common masses that appear as imaging "lesions" in the petrous apex, but their treatment modalities are very different. Accurate preoperative recognition by computed tomography and magnetic resonance imaging is, therefore, important for planning appropriate management strategies. We report a case with coexisting congenital cholesteatoma and asymmetric fatty marrow in the same petrous bone. The 2 lesions were indistinguishable on high-resolution computed tomographic images and were only identified on fat-suppressed magnetic resonance imaging sequences. This is the first report of these 2 lesions coexisting, leading to a rare misleading imaging finding.