Most gastric polyps are incidentally detected during endoscopic procedures, and this also applies to GA. They may grow in any part of the stomach and measure a few millimeters or several centimeters in diameter. Their designation as polyps implies that these tumors rise above the stomach lining. Indeed, the majority of GA are exophytic neoplasms, but about one in ten tumors is depressed relative to the surrounding mucosa [6]. GA typically possess a velvety surface and don't tend to bleed upon contact. They are most frequently solitary, while distinct gastric polyps without malignant potential as well as carcinoids and metastases are more likely to present as multiple lesions [3]. Furthermore, the presence of a pedicle as well as the absence of redness and surface erosions may imply a benign lesion, but these are not reliable parameters.

The vast majority of patients remains asymptomatic. Occasionally, GA may ulcerate and bleed, and patients may develop anemia. In rare cases, GA may provoke outflow obstructions and delayed gastric emptying [7].

Gastric polyps are detected endoscopically, but additional therapeutic measures are necessary to determine their nature. Histopathological analyses of tissue specimens may reveal whether a gastric polyp does indeed correspond to GA, and if so, which cell type prevails in this benign neoplasm. GA consist of dysplastic epithelium and contain goblet cells and/or Paneth cells - these tumors are defined as intestinal-type GA - or foveolar cells, which form gastric-type GA [3]. The former are more common and are more likely to harbor adenocarcinoma. Other classification systems consider the differentiation of low-grade tumors and high-grade GA [8] [9]. Parameters considered to this end comprise mitotic activity, nuclear anomalies like hyperchromasia, and architectural changes. Additionally, patients diagnosed with GA frequently suffer from gastric atrophy and intestinal metaplasia, and these conditions may also be confirmed histopathologically. In case of multiple lesions, it is strongly recommended to examine several tissue samples since different types of gastric polyps are known to coincide [10].

While gastric polyps are rather common findings in endoscopic procedures, few gastric polyps correspond to gastric adenoma (GA), a benign neoplasm sometimes also referred to as gastric adenomatous polyp [1] [2]. The distinction between subtypes of gastric polyps is of major therapeutic and prognostic relevance, though, since polyps without malignant potential may resemble precancerous lesions like GA, carcinoids and metastases [3]. In detail, neither hyperplastic polyps nor inflammatory fibrinoid polyps or hamartomatous polyps are likely to undergo malignant transformation, whereas the presence of gastric metastases does indicate an underlying malignancy. GA are known to be associated with concomitant adenocarcinoma, and they may undergo malignant transformation, but to date, it is not possible to predict such developments. Estimates regarding a GA patient's risk to suffer from adenocarcinoma vary largely and range from 2.5 to 50% [2]. Therefore, all GA should be resected. Regular follow-ups are an essential part of GA therapy and after the successful removal of the tumor, patients should undergo periodic endoscopy [4].

Patients suffering from Lynch syndrome, familial adenomatous polyposis, or MUTYH-associated polyposis are at increased risks of developing GA [5].

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