Heterotopic intestinal membrane in a retroperitoneal tumor.

Plain abdominal X-rays of a 13-year-old girl with chief complaints of back pain revealed calcification in the upper left abdomen. A calcified tumor was confirmed at the dorsal side of the pancreatic tail upon admission. A completely formed colic membrane free of all other germ layers was discovered within the tumor, leading to a diagnosis of heterotopic colonic membrane. To our knowledge, there have been no other cases of heterotopic intestinal tissue of this type, so we consider this an extremely rare case worth reporting.