We report a rare case of intussusception of the small intestine caused by lipoma with ectopic gastric mucosa including GCP within the inverted Meckel’s diverticulum.
Ectopic gastric mucosa originates from the transposition or invasive migration of gastric tissue, mutation and dysplasia of intestinal mucosa , and vitelline vascular origins in the fetal stage . The most common sites are the entire gastrointestinal tract and biliary system; onset is possible from any primitive gut site . Intussusception caused by the inverted Meckel’s diverticulum with ectopic gastric mucosa has been reported . As a characteristic of the inverted Meckel’s diverticulum, the morphology of the inverted Meckel’s diverticulum may involve serosal adipose tissue; it is often observed along with a mesentery containing adipose tissue, such as one crossing the ileal wall. If the diverticulum is inverted because of this, mesenteric adipose tissue is believed to be involved in the form of a lipoma . Consequently, connections to the mesenteric adipose tissue are observed. In our patient, the adipose tissue was solitary—tissues were found mainly in the submucosal layer without connections to the mesenteric adipose tissue. It has been reported that ectopic gastric mucosa of the gastrointestinal tract is associated with Meckel’s diverticulum, gastrointestinal duplication, or ectopic pancreas [12, 13]. Thus, we diagnosed ectopic gastric mucosa complicated with lipoma combined with the inverted Meckel’s diverticulum. Until now, there have been sporadic reports of the ectopic gastric mucosa in the small intestine caused by the intussusception; however, no reports on ectopic gastric mucosa with internal lipoma exist within the inverted Meckel’s diverticulum.
Polypoid mucosa in the gastrointestinal anastomoses of the remnant stomach has been reported as GCP ; pathological features include hyperplasic gastric pit epithelium, atrophy of corpus glands, hyperplasic pseudopyloric glands, and cystic dilatation; cysts are observed in the lamina propria and submucosa. However, a report on lesion onset at the gastrojejunostomy site after gastrectomy suggests GCP . Cysts with histologic features of GCP but confined to the lamina propria were distinguished from those invading from the muscularis mucosae to the submucosa, and the latter were proposed to be GCP. GCP are found in gastric remnants and caused by suturing and inflammation due to ischemia or reflux of duodenal fluid [14, 15]. Similar conditions in nonresected stomachs have been considered as GCP. Studies on heterozygous TGF-β1 knockout mice have shown GCP-like lesion onset , but a definite etiology is unknown.
Here, gastric crypt-like epithelium and dilated cystic glandular duct structures were observed in the lamina propria and submucosa. G cells did not produce gastrin in the pyloric antrum of the stomach, but CDX2 was expressed in epithelial cell nuclei in the intestine from the duodenum to the rectum . Mucins are classified as secreted gel-forming mucins (MUC2, MUC5AC, and MUC6), transmembrane mucins (MUC1), and others that are uncategorized . MUC1 is expressed on the apical surfaces of epithelial cells, MUC2 is a marker of intestinal phenotypic traits of goblet cells in the mucosa of both intestines becoming positive, and MUC5AC is expressed in gastric crypt epithelial cells .
MUC6 is expressed in gastric pyloric and cardiac glands, gastric accessory cells, duodenal Brunner glands, and esophageal cardiac glands . CDX2, MUC2, MUC5AC, and MUC6 confirmed the ectopic gastric crypt epithelium. This is an extremely rare case because GCP identification in ectopic gastric mucosa has not been reported. GCP is closely related to cancer; due to the high proliferative potential of GCP-component cells, they present along with cancer and some may be precancerous lesions [21, 22]. However, the pathogenesis is unknown. Thus, possible carcinogenesis was not ruled out; however, we consider it highly significant that we could resect the lesion.