Endolymphatic Sac Tumors and Papillary Adenocarcinoma of the Temporal Bone: Mahmood F. Mafee, MD, F.A.C.R1. Hemant Shah2, From 1. Professor and Head / Radiology University of Illinois at Chicago. 2. University of Illinois at Chicago. E-mail: mfmafee@uic.edu Role of MRI and CT

Abstract: Adenomatous Tumors of the temporal bone are rare. Benign adenomatous neoplasms (adenoma) of the middle ear are a distinctive benign tumor based on histological and clinical observations. Papillary adenocarcinomas of the temporal bone are invasive tumors. Although, the exact site of origin of these neoplasms is not identified, owing to the local bone destruction (usually centered at posterior petromastoid plate), the general consensus favors the endolymphatic sac as being the origin of these tumors. We present the computed tomography (CT) scan and magnetic resonance (MR) imaging features of papillary adenocarcinoma of the temporal bone. This report concerns a unique case in which histology was identical to papillary adenocarcinoma of endolymphatic sac, in which the sac and duct were normal on MR images and confirmed at surgery. To the best of our knowledge, this is the first report of such tumor that preoperative MRI demonstrated non-endolymphatic sac origin of a papillary adenocarcinoma of the temporal bone. The