Congratulations to Jenny Hong, MD, David Schrump, MD, and Marybeth Hughes, MD, of the National Cancer Institute, Bethesda, Maryland; they coauthored the winning Image of the Year for 2010. Their Image of the Month article on cystic parathyroid adenoma appeared in the July 2010 issue (Arch Surg. 2010;145:705-706; doi:10.1001/archsurg.2010.111-a). The images and text of this case should educate and interest surgeons of diverse specialties: general, endocrine, thoracic, and oncologic. This case also illustrates the usefulness of thorough reevaluation at the tertiary center. Inconsistencies were found in the sestamibi scan results, and the ionized calcium level showed a proportionally greater increase above normal limits than the intact parathyroid hormone level. At reevaluation, both findings strengthened the correct preoperative diagnosis of the mediastinal mass. The preliminary neck ultrasonography that indicated normal thyroid and parathyroids suggests either a deficiency in the ultrasonography or that the tumor was located in a supernumerary gland. The presentation of a parathyroid adenoma high in the posterior mediastinum is a reminder that the neck and mediastinum share common fascial planes and that mediastinal disease may have cervical origin either anatomic or embryologic. The gross operative specimen and the preoperative computed tomography image offer a valuable correlation.