Most of the gastric foveolar-type adenomas are related to hereditary tumor syndromes, such as familial adenomatous polyposis (FAP) and gastric adenocarcinoma and proximal gastric polyposis (GAPPS), and only a few sporadic cases have been reported [4, 5]. FAP is a series of syndromes including gastrointestinal polyps, cancer, and extracolonic lesion caused by germline mutations of the APC gene [3, 6]. GAPPS is considered to be a subtype of FAP, but has unique clinical manifestations [7]. The patient only underwent somatic mutation testing of the tumor, without performing germline mutation testing at the same time for personal reasons. Considering her age at onset (70 years old) and the absence of other gastrointestinal and systemic related lesions other than the gastric lesions, and no family history, we speculated that she was a patient of a sporadic gastric foverolar-type adenomas having concurrent presence of APC and KRAS somatic gene mutations. In addition, the somatic mutation abundance of APC and KRAS gene was 23.49% and 14.38%, respectively, which also tended to suggest that it was a sporadic case. Due to the rare occurrence, research on the molecular basis of sporadic gastric foveolar-type adenomas is limited. Some study about FAP-related gastric foveolar-type adenomas has reported somatic mutations in APC and KRAS [8]. It indicates that sporadic and syndromic gastric foveolar-type adenomas might share common genetic aberrations. We also tested several other gastric tumor and polyp related genes, involving PI3K/Akt, MAPK and Wnt/beta-catenin pathways (listed in the “Appendix”), but no other related gene mutations were found.

Some researchers believe that most adenomas are mucosal polypoid dysplasia that develops from chronic gastritis [9]. Except for being related to hereditary tumor syndrome, sporadic adenomas occurring in a non-inflammatory background are rare. Unlike the intestinal-type adenomas and pyloric gland adenomas related to H. pylori infection and atrophic gastritis [10], gastric foveolar-type adenoma often develops in healthy gastric mucosa and mostly occurs in the oxyntic gastric compartment (body/fundus), no matter it is sporadic or systemic. The case reported here was an adenoma that occurred in the mucosa at the junction of the gastric body/antrum, without obvious gland atrophy and H. pylori infection in the background. The adenoma tissue was diffusely positive for MUC5AC, while MUC6 was focally positive, indicating that the epithelium that composed the adenoma was a gastric foveolar phenotype. While the glands at the base of the adenoma showed diffuse staining of MUC6 but no gastrin staining, composed of columnar epithelium with only a small number of main cells scattered, indicating that it was a pseudopyloric gland metaplasia. Pseudopyloric gland metaplasia is considered to be related to inflammation and atrophy-related gastric mucosal repair [11], but in this case, there was no clear gastritis under endoscopy and microscope. The possible reason was that the patient was older (70 years old), due to the pyloric glands metaplasia of oxyntic mucosa with age, the line of gastric corpus/antrum junction was pushing forward the fundus of stomach. The morphology of this case enriches the performance of gastric foveolar-type adenoma, which can occur in the gastric mucosa of pseudopyloric gland metaplasia.

Sporadic gastric foveolar adenomas are extremely rare. The cases reported before are usually small, flat, or even depressed lesions located in the mucosa of gastric oxyntic glands. We reported here a protruding lesion with a maximum diameter of 2.3 cm, which caused symptoms of gastrointestinal bleeding. Recently, there is a study about a type of sporadic gastric foveolar-type adenoma with a raspberry-like appearance [5], which is considered as a special subtype of sporadic foveolar-type adenoma. The cases they reported were all located in the upper or middle stomach, and the mean lesion size was quite small at 3.2 ± 2.6 mm. Our case is the first case of a large-sized gastric foveolar adenoma developing at the junction of the gastric body/antrum.

The case also showed gastritis cystica profunda at the base of the tumor. The occurrence of gastritis cystica profunda is considered to be related to iatrogenic (surgical operation) infection, chronic ischemia, or inflammation, showing prolapse of the mucosa and glands to the muscularis mucosa and even the submucosa [12]. The deep-seated cystic gastritis at the base of the adenoma reported here may be related to the excessive size of the tumor causing chronic ischemia at the base. Gastritis cystica profunda at the base of adenomas is easily confused with adenocarcinoma [4]. But the deeply located glands were lack of cytological atypia and stromal desmoplasia, which could be differentiated from adenocarcinoma.

In summary, we reported a valuable case of sporadic gastric foveolar-type adenoma which occurred at the junction of gastric corpus/antrum in an elderly patient. The tumor was large in size and caused symptoms of upper gastrointestinal hemorrhage and accompanied by gastritis cystica profunda. This is different from the previously reported cases, which expands the clinical manifestations of gastric foveolar-type adenoma and increases the understanding of its morphology and molecular basis.

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