Gastric Polyps - Symptoms, Causes, Types, Diagnosis, Treatment

Gastric polyps are the distinct intraluminal protrusions of mucosal or sub-mucosal tissue. These polyps show proliferative development, which has the possibility of progressing into malignant tumors. Gastric polyps have multiple subsets, out of which, adenomatous polyps, characterised by low-grade glandular dysplasia; fundic gland polyps (FGP), characterised by dilated and irregularly developed fundic glands mostly lined by parietal cells with a smaller proportion of chief cells; and gastric hyperplastic polyps (GHP), characterised by pronounced foveolar hyperplasia, are the most commonly detected subsets of gastric polyps.

However, there is a much more comprehensive range of lesions that fall under the umbrella of gastric polyps: carcinoids, which are a grouping of endocrine cells leading to a projecting lesion; mesenchymal proliferations, which include gastrointestinal stromal tumors, leiomyoma, and fibroid polyps. These lesions can produce a mucosal/submucosal protrusion that manifests as a gastric polyp. Simple endoscopic observation is not always sufficient to determine the possible histopathology of a polyp; most of the time, biopsy and histopathologic evaluation is needed to recommend treatment and management.

Gastric polyps definition

Luminal lesions that protrude above the mucosal surface are commonly referred to as gastric polyps. These lesions are typically asymptomatic and small, and they are often found incidentally during endoscopic examinations or while diagnosing anaemia, gastrointestinal haemorrhage, or signs of gastric outlet obstruction.

Gastric polyps meaning

The word polyp is derived from the Greek words "polypus", which means "many-footed", and "gastric", which means "stomach". The term gastric polyp does not explain any specific aetiology but is merely descriptive. It can be used to identify any pedunculated stomach tumor, independent of its histologic nature, and has been applied to describe neoplasms, hyperplasia, and edematous formations. While a lot of benign stomach tumors can resemble polyps, most of them are adenomas.

Prevalence of gastric polyps

Although the prevalence and distribution of gastric polyps varies greatly throughout sources, It was revealed that between 2% to 6% of individuals undergoing endoscopy had gastric polyps. Gastric hyperplastic polyps account for 17% to 42% of those, fundic gland polyps for 37% to 77%, adenomas for 0.5% to 1%, and malignant neoplasms for roughly 1% to 2%. The fundus is where gastric polyps are most frequently discovered, and the prevalence rises with advancing age. The prevalence distribution greatly varies between genders as males are more likely to have adenoma, while females are more likely to have fundic polyps.

Incidence of gastric polyps

Gastric polyps are benign lesions that extend into the gastrointestinal cavity and have a broad base or pedicle. Nonetheless, the probability of gastric polyps transforming into malignant tumors varies based on the polyp's pathology, with an overall malignant transformation incidence of 0.4–10%. Reducing the risk of malignant cancer requires both active intervention and early diagnosis.

The incidence of gastric polyps is rising every year due to changes in people's diet and lifestyle, which also substantially raises the risk of cancer. Fundic gland polyps are slowly replacing hyperplastic polyps as a significant type of gastric polyp such that between 2000 and 2010, the percentage of fundic gland polyps increased from 8.8% to 66.1%, while the rate of hyperplastic polyps decreased from 48.5% to 20.8%.

Gastric polyps types

Based on the characteristics of the polyps, gastric polyps are majorly divided into:

• Epithelial polyps
• Mesenchymal polyps

Epithelial polyps are again sub divided into:

• Fundic gland polyps
• Hyperplastic polyps
• Adenomatous polyps
• Gastric neuroendocrine tumors

Mesenchymal polyps are sub classified as:

• Inflammatory fibroid polyps
• Gastrointestinal stromal tumors
  

Epithelial polyp

Epithelial polyps are the most frequent type of gut polyps. Some prominent epithelial polyps

are adenomatous polyps, hyperplastic polyps, and fundic gland polyps, each linked to a specific set of clinical contexts. Other non-common epithelial lesions that can manifest as polyps are neuroendocrine tumors (formerly known as carcinoids):

• Fundic Gland Polyps: Gastric fundic gland polyps are among the most often discovered stomach polyps (47%), showing up in 0.8% to 23% of endoscopies. These polyps occur in three different clinical contexts: syndromic polyps (familial adenomatous polyposis [FAP] syndrome), polyps linked to proton pump inhibitors use (PPI), and sporadic polyps. Although much larger polyps are also detected in all age groups, the 1 mm to 8 mm size lesions are more frequently found in middle-aged women. An activating mutation of the beta-catenin gene, which is involved in signalling pathways for cell growth, is the source of these polyps.
• Hyperplastic Polyps: After fundic gastric polyps, hyperplastic polyps are the second most prevalent type of gastric polyp. The phrase "inflammatory polyp," sometimes used inappropriately to refer to this polyp, should be avoided as it can be mistaken for inflammatory fibroid polyp (IFP), which requires different management. Less than 2 cm in diameter, sessile or pedunculated, hyperplastic polyps commonly form in the antrum, though they can occur anywhere. Inflammatory conditions like reactive or chemical gastritis, H pylori gastritis, chronic gastritis, and pernicious anaemia are closely linked to gastric hyperplastic polyps. It's interesting to note that while these polyps alone don't have much neoplastic potential, they are linked to a higher chance of synchronous cancer in other parts of the stomach mucosa, especially if chronic gastritis is present. It is unclear whether hyperplastic polyps should be endoscopically removed or just biopsied because of the low dysplastic capacity of these polyps and the possibility of simultaneous cancers.
• Adenomatous Polyps: As a precursor to stomach cancer, gastric adenomas, also known as gastric polypoid dysplasia, are real neoplasms. Their histological classification follows that of colon adenomas, with tubular, villous, and tubulovillous variations. They are usually solitary and can be anywhere in the stomach. However, they are most frequently found in the antrum. From an endoscopic perspective, they are typically sessile or fat instead of pedunculated. The development of these polyps is often linked to atrophic gastritis and intestinal metaplasia, but no clear correlation has been found with H pylori infection. Neoplasia is more likely to occur in polyps larger than 2 cm and with villous histology (28%–40%). Owing to the elevated likelihood of cancer linked to these polyps, guidelines recommend removing the adenoma entirely and conducting a thorough assessment of the entire stomach mucosa to detect any abnormalities; each of them ought to be biopsied. After resection, endoscopic screening is also necessary at six months (for partially removed polyps or high-grade dysplasia) or a year (for all other polyps).
• Gastric Neuroendocrine Tumors (Formerly Carcinoids): By immunohistochemistry, enterochromaffin-like cells (of which 90% are found in the corpus and fundus) stain with either synaptophysin or chromogranin-A and are the main component of the majority of gastric neuroendocrine tumors. In the stomach, there are four different forms of carcinoids, each with a unique prognosis and course of treatment. They also arise in diverse clinical situations. This specific tumor demonstrates the significance of performing simultaneous biopsies of the background fat mucosa. Endoscopically viewed, they resemble submucosal mass lesions, occasionally accompanied by ulcers. Several polyps are observed in clusters in type I and type II carcinoids, which almost exclusively arise in the body-fundic type mucosa. Type III lesions can appear anywhere in the stomach and are typically solitary. The prognosis is considerably worse for type IV carcinoids, which can occur anywhere in the stomach. Biopsies of the nonpolypoid mucosa are essential for determining the kind of tumor, prognosis, and course of treatment because histologically, these neuroendocrine tumors resemble the same.
  

Mesenchymal lesions broadly represent tumors generated from mesoderma. These polyps are usually found beneath the surface epithelium, giving the appearance of a nodule rather than polypoid. They can be found in the mucosa or submucosa. Endoscopic ultrasonography (EUS) and tissue acquisition should be used to further assess these lesions due to their deep placement. Some of the common mesenchymal polyps are gastrointestinal stromal tumors and inflammatory fibroid polyps.

• Inflammatory fibroid polyps: Inflammatory fibroid polyps typically manifest as nodules or polypoid lesions. These histologically distinct lesions originate in the submucosa and are characterised by edoema, inflammatory cells (primarily eosinophils), and spindle and stellate stromal cells that are positive for CD34. These are usually tiny (<1.5 cm) and sessile lesions that appear in the stomach pylorus or distal antrum. Although there have been a few cases of large gastric inflammatory fibroid Polyps producing gastric outlet obstruction, they rarely induce clinical symptoms. After initial histologic confirmation, no endoscopic follow-up is advised because these lesions are thought to have no malignant potential.
• Gastrointestinal Stromal Tumors: Gastrointestinal stromal tumors represent 1% to 3% of all malignant gastric tumors and are rare connective tissue tumors originating in the muscularis propria. During upper endoscopy procedures carried out for symptoms not related to tumors, the gastro intestinal stromal tumors are found often. The anatomic location, dimension, and aggressiveness of the cancer can all affect the clinical characteristics of this tumor. The stomach is the most ideal location for these tumors, though they can occur anywhere throughout the luminal gastrointestinal tract. The gastrointestinal tract's pacemaker cells are the source of these lesions. They are found in the space between the muscularis propria's inner circular and outer longitudinal layers.