This is a case study presented by the University of Pittsburgh Department of Pathology, which describes a 66 year old man who presented with a left thyroid mass. Visitors are given patient history, admission data, and gross and microscopic descriptions, including images, and are also given the opportunity to diagnose the patient. A "Final Diagnosis" section provides a discussion of the findings as well as references. This is an excellent resource for students in the health sciences to familiarize themselves with using patient history and laboratory results to diagnose disease. It is also a helpful site for educators to use to introduce or test student learning in endocrine pathology.