Adenocarcinoma originating from a completely isolated duplication cyst of the mesentery in an adult.

Alimentary tract duplications are uncommon congenital abnormalities that usually have an anatomical connection with some part of the gastrointestinal tract and have a common blood supply with the adjacent segment of intestine. A completely isolated duplication cyst (CIDC) is a very rare type of gastrointestinal duplication that does not communicate with the normal bowel segment and possesses its own exclusive blood supply. Only 5 CIDC cases in adults have been reported in the English medical literature. Additionally, only 1 case of mucinous cystadenoma from an infected CIDC of the ileum has been reported. This report describes a 52-year-old male patient with a peritoneal CIDC, which upon curative excision was found to have given rise to an adenocarcinoma. The latter was lined internally with malignant glandular cells and contained a smooth muscular outer layer as determined by microscopic examination of the tissue. We believe that this is the first reported case of an adenocarcinoma originating from a CIDC in an adult.