Electronic Clinical Challenges and Images in GI An Unusual Oral Mass Lorenzo Mannelli,* Mai Vi H. Hoang,* Annette P. Sabath, ‡ and Ken F. Linnau* Department of *Radiology and ‡ Pathology, University of Washington, Seattle, Washington Question: A 72-year-old man with a recent history of dental crown placement and a root canal procedure complained of right-sided mouth pain, numbness, and lip paresthesia. A mandibular lytic lesion was noted on orthopantomogram (Figure A, arrow) and magnetic resonance imaging (MRI) was subsequently requested. The patient was claustrophobic and the MRI was interrupted after the acquisition of the T1 and diffusion-weighted images. The MRI showed a 4  3.5-cm mass in the right masticator space, centered at and eroding the right mandibular condyle. The mass was hyperintense on T1-weighted images (Figure B, arrow), and showed restricted diffusion on the apparent diffusion coefﬁcient map obtained from diffusion weighted image (Figure C). A core biopsy was obtained (Figure D; H&E staining). Further, his past history revealed alcoholic cirrhosis and prostate carcinoma treated 10 years earlier with brachytherapy, remote history of basal cells carcinoma of the face. What is the diagnosis? See the GASTROENTEROLOGY web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. Conﬂicts of interest: The authors disclose no conﬂicts. © 2012 by the AGA Institute 0016-5085/$36.00 doi:10.1053/j.gastro.2011.08.047 GASTROENTEROLOGY 2012;142:e14 – e15