Duplication of the digestive organs in the retroperitoneum: a case report with reference to the importance of a standardized nomenclature and definition.

Duplications of the digestive organs, especially in the retroperitoneum, are rare malformations. We present the case of a 20-year-old man who had recurrent abdominal pain because of a solid and cystic mass located in the retroperitoneum, posterior to the pancreatic body. Preoperative diagnosis was difficult and a resection was performed. Histopathologically, intestinal mucosa, respiratory mucosa, aberrant pancreatic tissue, smooth muscle coat, and an external fibrous capsule were found. The mass was diagnosed as a duplication of the digestive organs. Findings in the pancreatic tissue indicated chronic pancreatitis and mild atypia in the pancreatic duct epithelium. Currently, many terms are used to describe these series of malformations, including duplication, foregut cyst, gastrointestinal duplication cyst, and enteric duplication cyst. Consequently, diagnosis and investigation can be difficult. In the atlas produced by the Armed Forces Institute of Pathology, duplication is used as a standardized diagnostic nomenclature with subclassification according to the site, but this has not been uniformly accepted. In addition, there are cases whose origins are unclear, especially in the retroperitoneum. In this report, we propose that the term duplication should be uniformly used for all cases in the digestive organs, and that they may then be distinguished according to their mechanisms.