The Arme Forces Institute of Pathology (AFIP) is a US government institution concerned with diagnostic consultation, education, and research. It was founded in 1862 as the Army Medical Museum and is located in Washington, DC on the grounds of the Walter Reed Army Medical Center. It primarily provides second opinion diagnostic consultations on pathologic specimens, e.g. biopsies, from military, veteran, and civilian medical, dental, and veterinary sources. The unique character of the AFIP rests in the expertise of its civilian and military staff of diagnostic pathologists whose daily work consists of the study of cases that are difficult to diagnose owing to their rarity or their variation from the ordinary. The accumulation of such cases has resulted in a rich repository of lesions, numbering over three million, that have been the basis of major pathological studies. Examples are the published reports on the clinical, pathological and molecular characteristics of the relatively newly recognized gastrointestinal stromal tumors by M. Miettinen and colleagues, e.g. Miettinen M, Sobin, LH, Lasota J. Gastrointestinal stromal tumors of the stomach. A clinicopathologic, immunohistochemical, and molecular genetic study of 1765 cases with long-term follow-up. Am J Surg Pathol 2005;29:52-68.